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Doesn't start when cold. Hard start when cold. It does

Doesn't start when cold ...

Doesn't start when cold

Mechanic's Assistant: Have you checked the battery, particularly the terminal connections? Are they corroded?

Hard start when cold. It does crank, battery is good.

Mechanic's Assistant: What is the model/year of your Audi?

2001 A4 1.8t AWM avant quattro

Mechanic's Assistant: What year is your Quattro?

2001

Mechanic's Assistant: Are you fixing your Quattro yourself? What have you tried so far?

Replaced spark plugs, ignition coils, CTS, cam sensor, crank sensor, combi-valve assembly, PCV valve and hoses, MAF and fuel injectors.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

And fuel regulator new fuel pump and filter about two years ago

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Customer reply replied 21 days ago
The only code the engine reads is P1479 35-10 Mechanical Failure - Intermittent for Break Boost Vacuum. Not worried about that. I also get some misfire codes when the engine does start because the intake seems to be loaded up with fuel by the time it starts. I found out that if I push the accelerator to the floor on start up it will start up quicker (less cranks but still to many cranks) because it shuts the fuel injectors off and allows the intake to clear out. So it's clear the plugs are fouling/flooding. Could an issue with the Secondary air pump issue be causing this hard starting condition? After I get the engine started, like immediately after I start the engine, I can shut the engine off then restart it with no problem, don't need to push the accelerator down.
Customer reply replied 21 days ago
If there was an issue with the secondary air pump, wouldn't I get some sort of engine code about it?
Customer reply replied 21 days ago
If the secondary air injection system has an effect on cold start, could the secondary air injection value have an issue? Bad diaphragm or clogged?
Customer reply replied 21 days ago
The car runs fine once I get it started. Seems low on power in the low RPM's, but it's always been line that since I bought the car (used). Before my cold hard start issue the car would every once in awhile not start on the first try. But always started by the second try. Then one day out of the blue the car just stop starting on first crank when cold.
Customer reply replied 21 days ago
I do have VCDS
Answered in 3 hours by:
5/29/2018
Danny
Danny, ASE Certified Technician
Category: Audi
Satisfied Customers: 4,474
Experience: ASE Master Certified with L1 Certification, Volkswagen Certified, VW and Audi repair shop owner
Verified
Your visit yes that's perfect so here's what we're going to do, the most likely thing that's going to cause this is a faulty coolant temperature sensor. It's a 4-pin Sensor 2 of which go to the engine computer and to which go to the coolant temperature gauge in the instrument cluster.You're going to go into the engine control module as well as the instrument cluster and then you're going to measured values and you're going to scroll up until you find the coolant temperature in each of the modules and if it varies by more than 10 degrees or the one in the engine computer is reading a temperature that it's not then you're going to replace it.Also once you get the vehicle running you want to read the mass air flow sensor value at both idle and 2000 RPM while the vehicle is stationary and it should read three and a half grams per second at idle and 10 and a half grams per second at 2000 RPM. If it reads Low at idle and fine at 2000 RPM then you have a vacuum leak from your Breather System and if it reads fine at idle and lower 2000 RPM then the mass airflow sensor is bad.I need any fault codes that the vehicle has, the code numbers please. I have never once seen secondary air cause this concern it's not EGR, it's the equivalent of the old smog pump on the Chevrolet's all it does is blow are into the exhaust on cold start to help heat the catalytic converter up more quickly. Even if the combi valves are stuck open the only thing that can happen is exhaust will come back up the valves into the airbox. That is unlikely to be happening, it would sound like it has an exhaust leak in the air filter housing.Since mass airflow sensor is generally read low and not high as in read LESS air than the engine is actually getting, and a vacuum leak will also cause less air to be read, it's unlikely to be the MAF and more likely to be the coolant temp sensor telling the vehicle it's really cold which is dumping too much fuel. The other possibility would be that the vacuum line to the fuel pressure regulator is broken and that's causing max fuel pressure even at idle. I'd be willing to bet it's just a temp sensor so let's just check that and if that's reading correctly per the outside air temp, then we will continue diagnosis.The temp sensor is on the back of the cylinder head in the coolant flange and has been superseded to a green with a yellow dot, the black sensors, and the green without a yellow dot are known bad items.If the wiring to the coolant temp sensor is damaged or it's unplugged then the system defaults to thinking it's negative 40 degrees, so check the wiring to the sensor for rodent damage.If I've answered your question to your satisfaction please remember to hit accept next to my name because that's the only way I get compensated for my time. If you need further assistance please let me know.
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Customer reply replied 21 days ago
Ive already replaced the coolant temp sensor and the fuel preasure regulator. If there is a wiring issue at the coolant temp sensor wouldnt the computer log an error? It doesnt. If wire is bad to coolant teml sensor are you saying the computer will report a negative 40 temp?
Customer reply replied 21 days ago
The MAF is new as well.

I understand you've replaced components, I didn't ask that, I want you to give me the readings, the readings of the MAF have a lot more to do with the way the vehicle is running. This is how diagnosis works.

You have a scan tool, we get readings to verify things are ok, you could have a bad part right out the box, and so that's why we test. You've also been replacing things and could have inadvertently knocked something loose, fried something, used the wrong component, gotten a bad one, etc.

So we need to check things over again. Generally if there's a wiring issue there will be a fault, however, not always, I've seen the vehicle have a failed temp sensor that allows pressurized coolant to be pushed into the wiring and owrk it's way all the way to the ecm or instrument cluster between the insulation and copper of the wiring, and nobody knows until it fries a module. It could just have SLIGHTLY high resistance that is causing it to thing it's 20 or 30 degrees colder than it is, and even that's enough to cause it.

Please run the tests I asked for.

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I want the temp sensor values from measured values in ECM and instrument cluster.

Measured value block 32 in the ECM which is fuel trims

Maybe watch measured value 14 and 15 real time cylinder misfires and see if one misfires more than the others when it happens.

The two main sensors that an ECM uses for fueling are the MAF and the coolant temp sensor, other than that it tailors the fuel trims using the wideband o2 sensor, but that takes 30 seconds or so to heat up, that's why even if you shut it RIGHT off, it fires back up. This indicates the o2 sensor is fine, and there's a problem with the initial fueling calculations strictly done with the MAF and coolant temp sensor, and the coolant temp sensor has a FAR larger impact on the fuel volume of a cold start than the MAF does, plus as stated the MAF reads low and results in LESS fuel, NEVER high because it's design, and the coolant temp sensor nearly always reads a colder temp than in actuality, resulting in MORE fuel.

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Customer reply replied 21 days ago
I found this, I assume these blocks are about the same for the 2001. http://www.ross-tech.com/vag-com/m_blocks/index.html
Customer reply replied 21 days ago
Regarding misfires, the computer usually logs cyl 3, but not always. The start issue is only when the engine has been setting for awhile and is cold. If there are issues with the MAF I would expect them to be present beyond just cold start. I do remember seeing some missing insulation on the wires on the coolant temp sensor plug. Back when I changed the sensor I coated the exposed wire with some RTV. There were actually a couple of wires that were exposed. I didn't think much of it at the time because the gauge in the dash reads correctly. There are four wires on that plug though, so I'm going to start with reading the temp values.
Customer reply replied 21 days ago
For coolant temp, what group should I be looking at and interpreting? http://www.ross-tech.com/vag-com/m_blocks/130-137.html

Coolant temp is in the first 10 blocks.

Listen, my specialty is diagnosis and tuning. I literally download the files from the ECM and modify them myself for more power. My sister drives a 04 GLI 1.8t with almost 300 hp, I drive a 98 VR6 jetta running the full engine management from the 4th generation Jetta with wideband and all, 6 speed swapped, with a supercharger putting down almost 400 hp.

If I didn't need info, I wouldn't ask for it. Most TECHS don't even understand how the ECM functions, I do. I'm asking for information because I need it, and you're making assumptions about whether or not YOU feel I need information, insistent that the MAF is fine, when I'm asking you for the MAF reading because I can determine MANY different issues with teh vehicle based on the reading.

So if you want to keep guessing then fine, but if you would just do what I asked you to do, I would already know what's wrong with your vehicle. And THEN you immediately start talking to me about messed up MAF wiring, which BY THE WAY THE READING WOULD HAVE TOLD ME AN HOUR AGO!

My youtube channel has 600k + views, I get paid by Continental and Pentosin to make videos for people, between that and this, that's ALL I do for a living, I'm not guessing, I NEED the information I asked for. Go into the engine module and scroll up in measured values starting at zero.

And THEN AGAIN, I ask you for real time misfire values because you have a scan tool capable of doing it and you respond with that it normally thorws a fault for cylinder 3, NOT what I asked, were you aware that sometimes it throws a fault for the completely wrong cylinder? And when you watch in value blocks 14, 15 , 16 sometimes another cylinder alltogether is misfiring worse? I don't have time to explain every single nuance of how these ECMs function, but there's not a person on here who knows more about ME7 engine electronics than I do. I have 6 of them sitting next to me on the floor with performance tunes on them, I use them like standalone, and I know EXACTLY how they should function, and if you'd just give me the information I asked you for, I'll tell you what's wrong with your car.

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Missing wires on the temp sensor plug is going to cause high resistance which is going to cause the vehicle to think it's colder than normal.

But I asked for the OTHER values because, that will make all 4 cylinders misfire, where a vacuum leak may not because airflow is not consistent across cylinders depending on the leak location. With the MAF numbers I can tell you if the maf is bad, if the breather is bad, if there's a vacuum leak, if there's a boost leak, if the wires to the maf might be bad, and a multitude of other things. I'm BEGGING you to use that hundreds of dollars scan tool for what it's intended so we can stop guessing. It takes me less than 2 minutes to diagnose a VW/Audi with VCDS in front of me. Literally!

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Customer reply replied 21 days ago
I'm not trying to avoid doing what you are asking me to do and never once have I questioned your experience. I gave you a link to the VCDS group code tables. Tell me exactly which values you want to see based on that so I can get them out of the VCDS tool for you. All those parts I changed were cheap and it's an old f**king car with shitty wiring in it......I'm a computer scientist and this car computer shit doesn't impress me at all because it's all fairly rudimentary computing technology. If you tell me exactly what you want out of the VCDS tool I'll give it to you...but you need to be more specific with your instructions.

Measured values 14, 15, 16 and 32

14 , 15, 16 are misfires in real time

32 is long term fuel trims

I think number 6 is the coolant temp but just scroll from 1 to 10 quickly, they're labeled. The MAF will also be in that top 10 and say g/s or grams per second.

I actually probably wouldn't even worry about where it's at in the instrument cluster I think you'll find a problem immediately in the ecm.

This was one of the first vehicles on the market with a wideband oxygen sensor, these computers are pretty damn advanced. They work like standalone, they can have antilag and no lift shift, miles ahead of what anybody else was doing at the time and still miles ahead of what most other brands are doing now. It's no quantum computer, but they're very advanced, very specific on their codes, and they even do calculations like what gear you're in with a manual transmission.

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These ECMS basically self tune themselves. You enter in the actual AFR, how much boost you want in absolute millibar, and bump the timing up and it self adapts timing +- 10 degrees, and calculates injector pulsewidth and everything on its own. To change to bigger injectors, you change two values, one for injector coil latency and one that's a formula of the orifice volume, and it does all the rest. They're amazing.

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Customer reply replied 21 days ago
Matrix math analysis programs and a hand full of I/O drivers, that's all these car computers are. When you modify the ECM you are simply changing the data matrix's...so you are not actually reprogramming them...you are simply changing the data the computer is allowed to use to make it's decisions. The computer sciency term for this activity is "configuration" not programming. I'm glad you have this experience though, because I've been suspecting that the previous owner of this car may have changed the program on the ECM. It also means you understand to some degree the program the computer runs and it's configuration data. This car has always had poor acceleration at low RPM, seems noticeably under powered. I contacted Ross-Tech about how to determine if ones ECM has a stock configuration. They said to dump out an AutoScan and send it to them.

Autoscan is worthless garbage. I hate that they always make people do that. And yes you're correct about configuring, but since we have to program the Eeprom, and it's encrypted with checksums, almost nobody knows how to do it. There's like 6 to 8 well known companies online that do it, and there's probably less than 100 people in the US that can modify these, most of them did their own vehicle only, and that's VERY few and far between, people like you generally. I'm in Washington State and I'm the only person I know of here who can do it.

You use a program called Nefmoto.com, it's completely free, there's a checksum correction app you run in cmd terminal as well. There are drivers for free for a program called tunerpro, also free, download Nefmoto, use your VCDS cable to pull the bin file out, you can email it to me or I can hook you up with the definition and stock file and you can look at the LAMFA map which is fueling, as well as a the boost map and timing map. You download the bin, then you can compare it in a hexeditor, or you can open it up in turnerpro with a definition file and look at the maps.

My file pulls about 7 degrees timing with 91 octane so when it gets colder or you get up to 96 octane it automatically increases ignition timing and performance. It smokes APR stage 2 tunes. I charge 150 bucks and do 4 or 5 a month, I also do immobilizer defeats.

I understand exactly how they run, not because I'm good at software but because I'm good with engine parameters. MAF flow to fuel 14.7:1 so if it's 14.7 grams per second of air it's 1 gram per second of fuel, then that's altered based on the coolant temperature sensor, though I'm not sure at what amount. The coolant temp sensor is an NTC thermistor.

Oxygen sensor comes online after about 30 seconds and is a true wideband sensor. Fueling is then modified up to 10% of the initial calculation to hit the AFR in the lamfa map based on two axis, RPM and desired engine load. As long as it can hit that AFR at a given boost, then all is well. So fueling can be Maf + CTS calculation +- 10 percent without a fault code and up to 25 percent to avoid engine damage at which point it reverts to an engine protection overfueling map as well as cutting boost back.

Ignition timing is constantly advancing up to the maximum in the timing map which is again rpm and load based. It can pull up to 10 degrees without a fault, and pull up to 25 to prevent damage at which point it can no longer adjust. It then monitors the knock sensors which are piezoelectric crystals for a certain frequency, and if it doesn't sense knock it bumps timing a degree and listens, then some more, and when it does it backs it off till there's no more knock and sets the base timing point there.

The MAF is a hot wire MAF which is heated to a certain temperature and monitored for that temp, as air flows past the wire cools, which requires more current to keep heated, and the system is calibrated to know that such and such voltage equals this much airflow. When the wire gets dirty the increased area and increased difficulty to heat said particles causes a drop in read air. The MAF features a burn off mode to heat it up and cook the crap off, it doesn't work well.

For every 11 degrees intake air temp reduction you gain 1% hp, and so if it's 80 degrees out and you're reading -40 degrees you're going to be running excessively rich to the point it can't adjust, and it WILL lack power.

My guess is you'll read the MAF reading and it's going to be reading 2.5 grams per second at idle and 7 at cruise, HALF what it should. This is resulting in a super lean mixture once the o2 sensor comes online, half as much fuel as necessary which is then retarding ignition timing, dumping excessive fuel, and possibly cutting back boost.

More than likely the breather hoses under your intake manifold are covered in oily residue because they're restricted by oil vapor sludge, which has plugged the PCV valve and suction jet pump, causing oil leaks from the back of the cylinder head and throwing off fuel trims. These need to be replaced about every 100k or your maf WILL read incorrectly.

Oreilly and Autozone sell these crappy "Bosch" remanufactured Mafs that are actually nothing Bosch about them other than the plastic pipe their crappy Taiwanese sensor that reads incorrectly right out the box is inserted in. The ONLY way they geet away with these ist because of the 10% +- trim window without a check engine light. My tunes literally WILL NOT run them because they don't react quickly enough, and they're generally off by a couple grams per second at wide open throttle right out the box. So I hope you didn't buy one of those, that's another reason I asked for the maf reading.

So if it's not the temp sensor causing the loss of power then it'll be low maf flow maybe. OH value block 115 is the boost specification and actual reading, you can verify that's correct. It's in absolute millibar, 1000 being atmospheric, yours will probably be requesting between 1600 and 1800. Make sure that's correct too. If it's requesting a lot less, then again the maf flow will probably mirror it.

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Customer reply replied 20 days ago
I'm on phone calls all morning.....ya it will be interesting to see what the sensors say. I think I can get the results and store to a file.
Customer reply replied 20 days ago
Regarding the PCV, I've replaced the valve and replaced all the tubing earlier this year, check valves and that suction jet pump thing. The breather/vent tube coming out of the engine seemed in good condition so I didn't replace it. I was able to buy a host assembly with all the check valves and suction jet pump in it. The PCV that was in it was all sludged up from condensation and oil. I've read about people who put catch cans on. Does that makes sense to do? Either way, changing it didn't seem to improve the acceleration or cold start issue.
Customer reply replied 20 days ago
When I get the temp sensor readings, do you want them with the engine cold or at operating temp?
Customer reply replied 20 days ago
I just went through and logged a bunch of results including the ones you are looking for. I warmed the engine up to operating temp first...but I didn't drive it, just driveway warm.

NOOOOO catch cans, I hate them, I'm honestly not even REALLY a fan of the 034motorsports molded silicon breather assembly which is what I am ASSUMING you're talking about. In my opinion because they're slightly different, they throw off the MAF readings a bit. But as far as catch cans, atmospheric ones REALLY cause poor MAF flow and also they don't run right.

I don't know if you've ever driven a custom turbocharged vehicle that was originally naturally aspirated, or even an older turbocharged vehicle from the 80s or early 90s. If you have you'll remember that they're very squirrelly, they build boost fast, have traction issues, and they don't transition well from vacuum to neutral intake pressure to boost.

That suction jet pump and crazy technical PCV valve are the reason this engine, despite having 180 hp (and even when tuning up to 300hp nearly on the stock turbo) is extremely refined, transitions effortlessly from a stop to any level of throttle application, doesn't burn out, doesn't feel like it's going to take off on you, you could put your 80 year old mother in it. I have friends with turbo Hondas with the 180 or 200 hp and they're frightening, try to rip the wheel out your hand with barely any throttle, but would still get walked on by your car. The breather system is all the key to that. I prefer to keep it with the factory breather system, except I do run the 710N diverter valve from the RS6, which is what nearly every site sells anyways now and doesn't much mention it.

You've mentioned the suction jet pump, what about the pancake valve on the back side of the motor, what about the elbow coming off the oil filter housing to the 3 way t piece with the PCV valve in it? You didn't mention those. While the jet pump IS important, its main function is to use the venturi effect to create brake vacuum using boost flowing through it horizontally to the brake booster line. The PCV valve, the "pancake" breather that is on the maf pipe to the turbo that one of those metal hoses on the passenger side goes to, and the diverter valve need to be done, as well as if you see a green and black or grey and black checkvalve up top. If you don't do those, it allows internal vacuum and boost leaks between the maf pipe, valvecover, and bottom end of the crankcase. This causes oil reversion, because oil vapor mixes with that air and every time the intake valves close on a cylinder that air bounces off like a wave and heads back to the air fillter housing. That kills the MAF.

It also causes boost air to leak past the rings, back up to the breather and to the crankcase (pancake) valve on the intake pipe, and it won't necessarily throw a fault, because it isn't leaking to atmosphere but it will cause a severe lack of power.

I had an 01 A4 once that felt like it gained 50 HP just doing the breather system.

I've attached a picture, is that what you changed? If so that's half the system.

When you do the breather repair, you really should drop the oil pan and take the valvecover off and clean the sludge out too, because your oil pump pickup is probably clogged. The vehicle DOES have a dynamic oil pressure sensor that grounds itself below 6 psi, and above 6 psi it's open circuit, and then again over 20psi pressure it also grounds itself. If you have over 2000 rpm and the sensor isn't seeing over 20psi oil pressure then it will turn the oil pressure light on, but the problem is that's at the oil filter housing, and sometimes you pull the pickup and when you shine a flashlight through the pickup it's so clogged you can't see the light through the screen, and that can cause incorrect camshaft timing. You theoretically should have a check engine light on for camshaft setpoiint not reached if that's the case, but things happen and maybe if it's only partially restricted, hitting its numbers but slowly, that could cause an issue?

They really need to be desludged every 100k miles and the breather system done as well, unless the person who owned it did their oil changes every 5 to 7k with GOOD synthetic oil. Poor quality oil and super extended oil changes and the breather bites it due to oil vapor sludge, and it takes the oil pressure with it.

You should find the coolant temp sensor reading in the engine computer and then view it when the engine is cold, start the vehicle and idle it at 2000 rpm while watching it linearly increase to the full 190 operating temp (85c I think?). Ive seen them go 40, 41, 42, 43, -40 degrees, 44, 45, etc so they can drop out on out at any time, and if that time is 70 degrees and that's what temp it is out, then you're out of luck.

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Is it 55 degrees there? Because it says when you started the car it was 13 C which is 55 degrees but yet your intake air temp is 33 degrees C which is 91 degrees, it seems unlikely you're drawing in 91 degree intake air from the front grill if it's 55 degrees out where you are...

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Customer reply replied 20 days ago
I also took some readings with the engine cold before I started it

It's cutting 25% fuel even though the maf is correctly reading 3.8 grams per second...

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Where do you live, what's the temperature there?

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Customer reply replied 20 days ago
Outside temp according to the cluster gage is 58F. I'm in altitude as well, fort collins, co. I think about 6000 feet up or something like that
Customer reply replied 20 days ago
I just went out and checked the temp. It's likely warmed up a few degrees since I starting reading the computer as well.
Customer reply replied 20 days ago
Fort Collins is more like 5000 ft up
Customer reply replied 20 days ago
I currently have iridium plugs in the car gaped to .25. Had it at .32 and tried a shorter gap to see if it had an effect on startup, I don't believe it did...I did this just yesterday. I'm considering changing the plugs to something more conventional.
Customer reply replied 20 days ago
regarding the temp difference that you see, is it possible the turbo warms up quick enough to raise the intake temp?

Ok, so a couple things. Why did secondary air abort? Why didn't evap run? Run basic setting 34, 36, those are run at like 1400 to 1900 rpm, your car may make you increase throttle until it says setting, or you may be able to hold the brake and throttle both all the way down and it does it on its own. After the O2 sensors set, run basic setting 71 and 70 to check for evap leaks. It looks like MAYBE the evap purge solenoid on the air filter housing is stuck open and allowing fuel tank vapors to be drawn in, espeically if the tank is full. MAF is fine, CTS is fine, but you're still getting WAY too much fuel and that's either from the EVAP system, or it's because you don't have vacuum to the fuel pressure regulator at idle which is necessary to drop the fuel pressure. Watch value block 31 short term fuel trim and see if it stops being -25% when you crimp the hose off for the evap purge solenoid.

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Customer reply replied 20 days ago
If I disconnect the evap line and plug it going to the engine, would that potentially change the cold start behavior if that is the issue?

Yes I think the temp stuff is in line, the injector pulse even looks inline, you either I believe have high fuel pressure, or you're sucking fuel tank vapors from a saturated evap charcoal canister. The purge solenoid is a 2 wire small solenoid with two vacuum hoses on the air filter, crimp that off and watch short term fuel trims in value block 31 and it should nearly immediately drop to near zero, not negative 25. If that doesn't work and you have a hand vacuum pump pull vacuum on the fuel pressure regulator, or at least remove that vacuum line at idle and see if you have a source of vacuum there, maybe it has a hole and no vacuum. I still don;t think that'd cause 25 percent.

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Customer reply replied 20 days ago
Both plausable....it definitely acts like the engine is getting to much fuel on start up.

It wpould but it's not necessary to wait for cold start. take vise grips and clamp it off, the short term fuel trims in value block 31 will IMMEDIATELY go from -25% (cutting 25% fuel based on your completely correct maf and cts readings which mean injector pulse width is correct, which I verified) your injectors are correctly pulsing 2 ms at idle yet you have 25% too much fuel and it's coming from either too much pressure due to no vacuum at the regulator or it's coming from that n80 valve (evap purge) which is a VERY common issue on the vehicle. If it has ever stalled on you after fueling up at the gas station then that's definitely the issue.

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Customer reply replied 20 days ago
I've got a vacuum tester.
Customer reply replied 20 days ago
It's never stalled on me after fueling

Cool hook it inline with the fuel pressure regulator and it needs 19 inches of vacuum at idle, if you can apply that with the hand pump, then do so and check it as well. If applying vacuum does nothing, and clamping the n80 valve does nothing, then you need to run a fuel pressure test. Some fuel filters have regulators built into them, it's possible the wrong filter was installed, or possibly the hoses to it were hooked up incorrectly, that can cause this I've done it.

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Only cylinder 3 and 4 are misfiring and 4 is worse, that's at the back of the fuel rail, which is where pressure builds first due to it deadheadding at the back of the rail, 3 and 4 will have higher fuel pressure than 1 and 2, so it's quite possible that it's the fuel pressure. I would expect more even misfiring from evap, it would be better mixed and more evenly distributed with the airflow.

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You said you changed the regulator, you didn't install a 4.5 bar regulator in place when the factory stock was a 3.5 bar did you? That coupled with no vacuum to it would REALLY cause this. 70 PSI instead of 30 psi at idle.....Look at the numbers on the regulator and make sure you didn't put the bigger one in, if you did swap back to the 3.5 bar and see if it gets a little bit better.

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Customer reply replied 20 days ago
group/block 31 doesn't show fuel trim
Customer reply replied 20 days ago
there is 107 lambda control bank 1 -25%
Customer reply replied 20 days ago
Group 107 value, I blocked off the hose coming into the purge valve from the canister (hose coming up from the fender side) and that lambda value didn't change. I'm going to see if I can figure out what I put in there for regulator, but from what I understand it's a stock rating.
Customer reply replied 20 days ago
pressure regulator holds vacuum, vacuum line is in good shape and has no obstruction to intake. Regulator not leaking fuel from vacuum side. Pressure rating is 51psi. This is what's in it. https://www.ebay.com/p/Fuel-Injection-Pressure-Regulator-BWD-24109/81157580?iid=273101062715&chn=ps
Customer reply replied 20 days ago
the car used to start correctly back when the fuel filter was changed...so if it's the fuel filter causing a high pressure situation where the regulator cannot compensate then the fuel filter would have had to fail after the fact.
Customer reply replied 20 days ago
I have a fuel pressure test gauge, but not sure if I can hook it up to this system. What pressure should the fuel be at?
Customer reply replied 20 days ago
30psi at idle right?
Customer reply replied 20 days ago
I checked idle vacuum and it's at 15psi. I used the vacuum tester to pump the FPR down to 19psi. That lambda value went from -25% to like -23.x%. I applied as much vacuum as I could only got it down to -22.x%. I believe you may be right about the fuel pressure from the pump being high. Is it possible for a fuel pump to produce more pressure at some point then when it was new? The pump is only a few years old...the filter is only a few years old as well.

That's a Borg Warner very aftermarket regulator. 51 psi IS 3.5 bar. There are two different thermostats, 3.5 bar, and 4.5 bar and you're supposed to look at the original, it has writing on it. This aftermarket one does not.

I'm racking my brain here, you're running rich, absolutely running extremely rich, the question is WHY....Is there any change in the way it runs when you hook a vacuum pump up to the regulator, and you start off with running at idle with no vacuum to the regulator and then pull vacuum on it? Because I know what the injector pulsewidth should be, and it should definitely be around 2 ms, somehow you're getting a ton of extra fuel, but the two most important sensors that deal with that are reading correctly. The fueling is almost exlusively calculated based on the MAF flow and coolant temp, that calculates injector pulsewidth. If injector pulsewidth is fine, but it's still running rich, it has to then have high fuel pressure, or maybe you have leaking fuel injectors??? That's a thought. The fuel rail is very easy to pull on this, maybe you should try to pull the fuel rail and observe the injector spray pattern, and whether or not they leak down fuel? Maybe they're gunked up and the pintle isn't sealing?

You CAN adapt a fuel pressure gauge to this, I even use a cheapo harbor freight one I think...actually come to think of it you know what I did? I went to the junkyard and got another fuel rail and the hose end, and then I cut the fuel rail so I could attach a gauge to it, then that can connect to the line from the pump, and then I run a cut off hose that connects to the fuel rail (just like the one on the car) but I have it clamped to the piece of fuel rail I'm using to bridge the gap.

Do you have the old regulator? Before you go and pull the rail I would just for the heck of it replace the old one back in. Maybe the seal on this one is junk, the way it works is vacuum literally pulls up on the plunger in the middle and opens the hole in the fuel rail so it can return to the rear of the vehicle. Maybe it's bound down in there and it's never pulling up to open the hole, and that is forcing all of the fuel to just stay in the rail deadheaded....

Try crimping the fuel return line and see if there's a change in the way it runs? If that's not it that'll likely make it stall out. If you crimp the return line and nothing happens, then put the old regulator back in. I haven't been this stumped in a while, I know we're overlooking something.

Another thing I was thinking is that the throttle body is at 1.5 degrees which is pretty far shut, try maybe cleaning the mechanical portion of the throttle body out with a rag, here's a video I made showing how to clean the electronic side too.

https://www.youtube.com/watch?v=YcmA2Yc3JJw

Then run basic setting 60 to readapt the throttle body when done. Maybe there's so much gunk blocking the throttle plate that the engine isn't getting enough air past the throttle plate, the thing is that it should show up that way then with the MAF flow, but with how shut it is at 1.5 degrees it seems to indicate that it's trying to close the airflow off for some reason.

We DEFINITELY have not enough air, or too much fuel. Relative to each other it's the same thing but I'm trying like hell to figure out which of the two and devise tests for you to go with the limited equipment you have....

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Ok wait, you state 15 psi....vacuum is GENERALLY measured in inches of mercury, and should be 19 inches of vacuum. If you actually do have a gauge that reads negative PSI, then 15 negative psi is 30 inches of vacuum, which is WAY too much, and that WOULD indicate that you've got a lack of airflow and point toward a dirty throttle body....

If you are actually reading 15 inches of vacuum however, then THAT is too low, it should be 19 and that indicates a vacuum leak, so which is the gauge in?

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It DOES seem to point toward a vacuum leak because when you apply 22 inches of vacuum which is much more like what it SHOULD be, it does lean it out slightly. I'm trying to figure out how the hell you could have a properly reading maf, and then still have a vacuum leak....unless your maf is the wrong one and reading too high somehow, the ONLY way I see that happening is if the housing size is different, if you put a 2 inch housing in when it's supposed to be 2.5 (which I dunno if that's an option or not) then you would be reading more air than is actually entering the engine, and OVERFUELING, and still could have a vacuum leak....

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Customer reply replied 20 days ago
I replaced the injectors last week thinking I had one leaking off after shutdown, etc...no change. The car wouldn't start when the original regulator was in it, putting a new one in it didn't change anything. I cleaned and adapted the throttle last week, no change. Didn't clean electronics side so I'll watch your video. I wondered about the throttle due to the poor acceleration, but never got any throttle codes, etc...so after cleaning and adaptation I figured it was fine..it had a bit of a gunk ridge but far from bad. I know there are gears in the throttle actuator, maybe the throttle plate is moving to slow or something or to far shut, not running lean enough? Searching for a vacuum leak on this car looks like a really fun activity.
Customer reply replied 20 days ago
My vacuum gauge is on a hand vacuum pump so it's a negative gauge, so I guess that means vacuum is not an issue?
Customer reply replied 20 days ago
could the vacuum line between the regulator and intake be restricted or collapsing in a way that is unnoticeable?
Customer reply replied 20 days ago
Is it possible someone tuned this ECU and did a shitty job of it?
Customer reply replied 20 days ago
The MAF I changed was the same size tube as the one I took out, which I think the original was audi.
Customer reply replied 20 days ago
Can a throttle body actuator cause issues with air flow and not cause engine error codes?
Customer reply replied 20 days ago
Just wondering if maybe the throttle body actuator is the issue with the poor acceleration as well. If the teeth are worn could that be leaving the throttle plate in a lower position always then it should be?
Customer reply replied 20 days ago
But error codes would come from gears not moving when they are supposed to.
Customer reply replied 20 days ago
MAF is 2.5 inch
Customer reply replied 20 days ago
34;It DOES seem to point toward a vacuum leak because when you apply 22 inches of vacuum which is much more like what it SHOULD be, it does lean it out slightly." - leans out slightly....but maybe that's because not enough air is coming into the engine in general?...in general range to where the throttle plate is?...maybe the controller in the throttle thinks the plate is in a position that it's not, even after adaptation. Is it possible to distort the plate position in relation to the position sensor (those linear pots inside).
Customer reply replied 20 days ago
looks like there is a sensor of some kind on the top of the intercooler....what is that?

That's a map sensor used only as a boost pressure sensor.

So, it's highly unlikely the throttle is in the incorrect position and unaware. The throttle body and throttle pedal each feature inversely proportional 5v potentiometers. One sweeps 0 to 5v as the plate opens, the other sweeps 5 to 0v as the plate opens, the signals are compared, when one puts out 4 volts the other puts out 1, if that doesn't match it knows. This makes unintended accelleration impossible, and it makes the throttle being in the wrong position basically impossible unless the ECM throttle body driver is faulty.

I don't think a shitty tune would cause this, mostly because how I explained it. Remember we talked about how it's sort of recalibrating. There's a map, you put in what AFR you want the vehicle to have. The computer knows does a formula that's similar to Maf flow / (9 + Lambda) x CTS compensation factor x (Injector orifice area and fuel pressure formula to calculate flow rate in ms)

And then the Wideband reads it, and adds or subtracts a percentage trying to get back to the correct AFR. So if he changes AFR, even if it's lean or rich, then it wouldn't be pulling fuel, because it would be targeting his new number. So if he put in say 10:1 AFR, then right now, based on the fueling it's doing, you'd have 0 for short and long term fuel trims.

If he upped the boost, it would be fast, and it would only be fast if it could hit the proper AFR, which it's running rich, so it WOULD be boosting 20+ psi.

So really unless they messed with the MAF scaling, there's just no way for this to happen...

Out of curiousity....you didn't possibly install the MAF backwards did you? I think it's maybe a possibility but I don't know what would happen.

https://www.youtube.com/watch?v=VNfa9mKM_-4

There's a video about tuning, it's like 20 minutes long, it shows EXACTLY what's inside the ECM, being that you're into software this will probably help you understand where I'm going, and why I'm focused on what I am.

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Customer reply replied 20 days ago
Makes sense about the throttle....so if it's not logging errors and the throttle plate is likely not off enough because of worn gear teeth then is there any reason to take it back off again and clean it?
Customer reply replied 20 days ago
How could we check if they messed with the MAF scaling? Download the bin file?
Customer reply replied 20 days ago
MAF sensor is in correct direction, can only go in one way I believe.
Customer reply replied 20 days ago
Interesting video...I did some setup work for my dad's drag car a number of years ago. That was just ignition control and transmission shifting.
Customer reply replied 20 days ago
the goal then here is to try to figure out how to get that fuel lambda value down to 0%? Or near it?
Customer reply replied 20 days ago
im messing with trying to affect that lambda value. i take the vacuum hose off between intake and FPR it goes to -10%, it's leaking vacuum at this point. I plug the vacuum and it goes back to -25%. I plug the vacuum leak and pump down the FPR with my vacuum tester and it goes back to 25%. I unplug the vacuum at the manifold but leave the FPR pumped down around -15psi and then I get .8% on the lambda value. So the computer likes the vacuum leak. Bad throttle body?
Customer reply replied 20 days ago
Something else i noticed. It doesn't go to 25% lambda right on start up. Comes on later...like a minute or so later
Customer reply replied 20 days ago
when I the gas it goes to 0% like I guess it should. Are you sure -25% is not normal?
Customer reply replied 20 days ago
My fuel pressure tester does not fit, went up to parts store, they don't have anything...so I'll have to come up with something to test fuel pressure
Customer reply replied 20 days ago
When cold the fuel lambda is 0, as it warms up it goes to -25%. If I disconnect the fuel pressure regulator from the intake, let the intake vent/leak and use my hand vacuum pump to pump down the FPR I can get the lambda value close to 0

Ok, wait, so you're stating you plug the vacuum leak and you then pull vacuum on the FPR and you get 25%. Is that SHORT TERM?

Let me explain the fuel trims. Your initial value of -10% is -10% short term, over time that -10 will become -8% short term and long term will be -2% (for a total of 10), then short term becomes -5 and long term is -5, eventually short term is 0 indicating that it has finally effectively fixed the fuel trims, and long term is at -10% meaning the ECM does the MAF + CTS calculation - 10% and THEN when it checks with the wideband it's perfect.

When you state, you plug the vacuum leak and pump the FPR vacuum it goes back to 25%, do you mean -25 % or positive 25%?

Can you take a picture of your vacuum pump gauge please. I really need to be clear what we're talking about here.

The only reason that your vehicle would LIKE a vacuum leak is because you have excessive fuel, and the fact that it makes a difference means there isn't one. I still REALLY think you need to figure a way to do a fuel pressure test, I think your pressure is high, I don't know why, whether the regulator is in wrong or just a piece of junk, but I don't trust it. It doesn't feel right to me, the ONLY way you're able to get it to work is by introducing too much air and then manually pulling excessive vacuum to drop the pressure lower than intake vacuum alone can do.

You gotta figure out how to do the fuel pressure test.

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Customer reply replied 20 days ago
Agreed. Typo on the 25...i meant -25
Customer reply replied 20 days ago
Im foing to take it to a local shop and have them test the pressure

They're going to charge you 100 dollars you can buy a fuel pressure test kit a harbor freight

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Customer reply replied 20 days ago
I have a fuel pressure kit from harbor freight but it doesn't have fittings that allow me to tee into the fuel supply line.
Customer reply replied 20 days ago
I just have this pressure tester. https://www.harborfreight.com/Fuel-Injection-Pump-Tester-62623.html

That's the same kit I used at my shop for years, You tried all those connections? Do you have a pick and pull wrecking yard near you? I would go get the fuel rail if I were you and hack it up like I described, you cut the end of the rail with the threaded fitting off and you screw that to your fuel line, and then you use the piece of hose included in the kit to go from the rail to the straight silver piece (you need the fuel line too from the yard) and then you take the piece of the fuel line from the yard and go from the other side of the silver T for the valve, screw it on, and then crew the cut off line from the other car into your cars fuel rail and now you have a pressure tester in line.

Did you ever try putting the factory FPR back in? In 8 years of owning a shop and 18 years working on these cars I've NEVER ONCE had to replace the fuel pressure regulator, I'd return that if you can, put the original in.

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Oh yeah and about your gauge, if you look the scale on the bottom left says in hg, that's inches of mercury like I was stating.

Fuel pressure regulators work linearly, every lb of boost gives you another lb of fuel pressure, and every inch of vacuum subtracts that much fuel pressure, you're pulling 25 inches of vaccuum to get it to balance out and that's removing 14 psi of fuel pressure, 7 more than it normally would or something like that plus adding air. That almost certainly means the pressure is high. I think you need to ditch that janky aftermarket regulator.

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Customer reply replied 20 days ago
I have the original...I'll go pop it in later this morning and see how that lambda value reads. If it's still off I'll take it over to the shop to get a pressure reading. Exactly what value(s) should I be reading regarding the fuel trim lambda?
Customer reply replied 20 days ago
all the pressure readings I was giving you are in psi
Customer reply replied 20 days ago
Think a plugged up pcv system is causing high vacuum?

No, your vacuum gauge is NOT in psi, read it again. The red numbers are kilopascals and the others are inches of mercury, what scale were you using?

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Customer reply replied 19 days ago
I took out the new FPR and the small o-ring had a rip in it, but not all the way through, just like it got shaved a bit...likely during install. While maybe this was causing fuel to leak, which I doubt because it was tight fitting, the car was still hard to start while the original FPR was in it. The original FPR screen is bad so I'm not putting that one back in the car....I also have to get a new FPR or oring for the new one as well.
Customer reply replied 19 days ago
I believe enough of the oring on the new FPR was shaved off to possibly allow a leak. If the fuel system is pressurized up to the rail at above 50psi it very well could have leaked past the small oring and added another 10 or more psi to the overall pressure. Looking at the old FPR the small oring is well compressed and a bit hard (likely from sitting out of fuel) and I guess it's possible that oring may have been leaking a bit as well. I wonder if I can/should just try to replace the oring on the new FPR (screen on old FPR unusable)?
Customer reply replied 19 days ago
This part I actually got from a local parts store and it has a life-time warranty on it. They will have the part this afternoon so I'm just going to exchange it for a new one and try again. I'm pretty sure I oiled the orings before I installed the last one, I think that oring is just a bit to large for the inner tube where the FPR sits on the fuel rail. Hopefully this answers the fuel pressure question.
Customer reply replied 19 days ago
Here is a picture of the new FPR with the oring sliced on one side...pretty sure that would let additional fuel pressure bypass into the rail. I'll install the new one and if we get the same results I'll pull it out and see if it cut the new oring again...if so I'm going to take it back to the store, get my money back then buy a different brand.
Customer reply replied 19 days ago
I think I used a bit of bearing grease when I installed it last time. I'm going to try motor oil next time. I'm just going to oil the piss out of everything, fuel rail tube as well.
Customer reply replied 19 days ago
I was reading inHg...sorry
Customer reply replied 19 days ago
Got the new fuel pressure regulator. Oiled it up and put it in. Turned the car on hooked up the computer and watched Group 107 Fuel Injection (Fuel Supply System) Lambda Control Bank 1. When cold it's 0%, which it was. Warmed up a bit and watched it slowly count down to about -18%. Took it out for a drive, got it up to operating temp. At the stop sign it was -25%. Under acceleration it was somewhere between -8% and -14%. When I would stop again it would be back at -25%. Not sure how well it starts now because the fuel rail had no fuel in it. Going to let it cool down to see if it starts correctly later. Group 32 Lambda Control (Mixture Adaptation) was at Adaptation (Idle) Bank 1 Sensor 1 -2.4% and Adaptation (partial) Bank 1 Sensor 1 -2.3% right before I shut it down. If it's a hard start again I will take it over tomorrow to get the fuel pressure tested. I don't believe the 2001 A4's had FPR in the fuel filter, I think it was later models that did. You may know better then I.
Customer reply replied 19 days ago
FYI...I took the FPR back out again to make sure I didn't booger up the oring and it was good.
Customer reply replied 19 days ago
Have you ever heard of this? http://usbip.sourceforge.net/
Customer reply replied 19 days ago
I wonder if it would be possible to put my car on the Internet and then let you access it directly by running VCDS on your computer.
Customer reply replied 19 days ago
If I have time tonight I can mock it up in my lab to see if it will work.
Customer reply replied 19 days ago
basically I would connect a computer to the car then basically host my USB port (the one connecting to the car using the Ross-Tech cable I have). Then you would install a special USB drive (I believe, I still have to read the doc) then you basically connect VCDS up to the virtual USB port on your computer that routes over the internet to my car. I think it will work.
Customer reply replied 19 days ago
Tried out the usbip tool and it's buggy on windows...may not always work. Seems like it was not fully tested before release.
Customer reply replied 19 days ago
I'm going to clean out the PCV system this evening. If that's clogged could it lead to a rich condition?
Customer reply replied 19 days ago
I'm thinking if the PCV is plugged/closed this may cause a high vacuum situation? Allowing the vacuum leak earlier kind of simulated (but not fully in terms of +/- vacuum differential with crankcase) a working PCV system I suspect.
Customer reply replied 19 days ago
Not sure how interested you are in this but after cleaning the PCV I took it for a drive and logged data as I drove. Not sure if the values are useful...but if there are specific values you would like to see while the car is being driven let me know.
Customer reply replied 18 days ago
Was just thinking....would an issue with barometric pressure sensor cause high fuel pressure? I live about 5000 ft above sea level.
Customer reply replied 18 days ago
My issue is a hard start when cold. Is barometric pressure a factor in fuel trim in open loop mode?
Customer reply replied 18 days ago
I'm wondering if the BARO sensor is not sending the right signal to the computer and causing it to think it's at a different altitude then it actually is.
Customer reply replied 18 days ago
BARO sensor is reporting the correct value for the altitude.
Customer reply replied 18 days ago
Could a restricted fuel return line cause a higher pressure? I'm taking it into the shop tomorrow to get the pressure checked.
Customer reply replied 18 days ago
I was able to put my fuel pressure gauge on the return line and it's got very low pressure so I do not suspect anything in the return line is restricting/raising the fuel pressure.
Customer reply replied 16 days ago
I took the car to the shop yesterday and had them check the pressure. It's up around 70psi and it doesn't hold after shutting the car down. I'm having them change the fuel pump since it's still under warranty. I should have it back Monday or Tuesday. I'm fairly confident this will solve the issue. Thanks for your help I appreciate it.
Customer reply replied 13 days ago
Got the car back from the shop today. They replaced the fuel pump. The FPR holds pressure in the fuel rail, runs at about 65psi, goes up to 68psi when you take the vacuum line off the regulator. When the engine is shut down the fuel pressure leaks off back through the supply line, it's down to 10psi within a minute after shutdown. The new fuel pump is likely fine, but the car is still using the original fuel pump assembly cap and fuel line to the pump. I'm suspecting maybe I have some sort of leak at the fuel line. It's a 8D0201351A. Have you ever encountered issues with the in-tank fuel lines on these A4's?
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audi a6 2011 c64f no power on AC compressor JA: Is the power loss consistent, or does it fluctuate? Customer: consistent JA: Are you fixing your A6 yourself? What have you tried so far? Customer: loca… read more
Michael Partington
Michael Partington
Auto Electrician
High School or GED
603 satisfied customers
2001 Audi A4 Quattro - had been sitting for over a month.
2001 Audi A4 Quattro - had been sitting for over a month. When I went to unlock the car and the alarm/hazard lights went off and I couldn't turn it off. Tried turning on the car, hoping it would go of… read more
Michael Partington
Michael Partington
Auto Electrician
High School or GED
603 satisfied customers
I have a 2012 A4 Quattro changed the calipers / pads /
I have a 2012 A4 Quattro changed the calipers / pads / rotors now when in stop & go traffic the brake pedal gets too hard & doesn't want to stop the car but after I press the gas pedal and go back to … read more
Kevin
Kevin
workshop foreman /master tech/mot tester
1 satisfied customers
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Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

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