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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8610
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi Galant GTS: I have an 05 Gallant GTS. 3,8L when

Customer Question

I have an 05 Gallant GTS. 3,8L when starting the car the car runs up around 1kRPM. After driving for an extended period of time the check engine light will come on and being to idle around 750-800. Once driven to a typical operating temp the car will stutter when launching from a stop and appear to struggle and choke, up into about 40 where it retains it's normal operation. The engine codes thrown are low threshold from the cat bank 1-2. And low voltage on the 02. I feel that neither would cause this issue. Could it be a possible TPS or IAC?
Submitted: 2 years ago.
Category: Mitsubishi
Expert:  Doug replied 2 years ago.
Hi,
It sounds like you are on the right track with your thinking, the problem though is that this vehicle doesn't have an IAC or a TPS.... they are both built in to the logic in the electronic throttle body.
When was the last time the throttle body was thoroughly cleaned? Recalibrated?
Customer: replied 2 years ago.
I bought the car recently it has about 178k on it and to my knowledge of has never been done. The MAF was swapped though due to what the old owner said was a failed MAF, which I have researched is common in my model?
Expert:  Doug replied 2 years ago.
They do fail from time to time... considering this replacement that might be an area worth investigating to make sure it is the right MAF for the car and not an aftermarket one (This era Mitsubishi does -not- get along with aftermarket electronics).
Are you able to do minor work/inspections on the car? If so, can you get the part numbers off the MAF (located on the intake hose, just behind the air filter box)? How about pulling the intake hose and getting a good view inside the throttle body to check the conditions?
Customer: replied 2 years ago.
Ya km very mehincally inclined. That how j notice the vac line not connected to the intake. I'll pull the intake tubing off now. Snag the MAF part #, old owner said it was off another mitsu. And ill take a look at the TB & butterfly. Could it be the MAP as well? Just wondering cause unless the car is hot hot, as in run for more then hr or so it jumps off the line fine when given gas its strictly when its hot.
Customer: replied 2 years ago.
Maf # ***** believe is :
MR985187
Made in japan (pbt-gf30)
Expert:  Doug replied 2 years ago.
Great.
The MAF is the right one, and with a Mitsubishi number printed on it so that is good too. That's not to say it is working, but odds are it is OK if you aren't seeing any actual MAF related faults.
Lets pull the intake hose off and get a good look in that throttle. If it is gummed up decently I can see it causing hot operation problems.
You will need a 10mm socket/ratchet to loosen the hose clamps then pull the hose off. Then either have the key OFF and use your finger to open the throttle while looking in with a flash light, or have a helper apply the gas pedal with the key on to automatically open it. Do not try to prop the gas pedal or anything though, as the throttle could seriously hurt your fingers if it were to snap shut under power.
Take a look in there and let me know what you see.... we are wanting it to be darn near spotless. The build up is in thousandths of an inch when it starts causing problems.
Customer: replied 2 years ago.
Awesome, will pull it off tomorrow morning and update you. Would u recommend not driving it? I have the possibility to bring a different car home but would rather work on it in the garage at home. Mostly highway, would u recommend not driving/driving? No harm no foul either way?
Expert:  Doug replied 2 years ago.
I apologize for the delay, I am having some connection issues at the moment.
I would definitely do that inspection and the most likely necessary cleaning as a priority before driving anywhere more than a few miles. The consideration being that if there is a more sinister issue (Throttle body failure pending would be my suspicion), you don't want to risk it worsening and getting stranded somewhere.
If you only have a few miles to drive, you could give it a go before trying anything. If you are talking 20 miles etc... I would only try this if you are OK with a possible tow. Again this would be worst case scenario.
If you can do the cleaning first and compare behavior that would be ideal... and of course the same would apply if the problem maintains; only drive longer distance if you are OK with a potential tow if it worsens.
Hopefully the drive is short and you can limp it home for work tomorrow of course... and then ideally the cleaning takes care of it. If the cleaning does not help (or it is spotless etc), then I would definitely want to get it on a scan tool (not a code reader) to see what is going on in that throttle when the problem is occurring and proceed from there.
I will be in through the evening and tomorrow as well if we need to talk more about this; I'm going to see if I can figure out what is going on with my internet service right now so there may be a bit of a delay again while I have stuff reset etc, but I will be here more tonight.
Customer: replied 2 years ago.
I have it off now, and off the bat it doesn't appear its sitting completely flat. I have not tried to turn it on at all but is this normal.
Customer: replied 2 years ago.
I can proceed if it doesn't matter at rest, no ignition just sitting. Had run about an hr ago with the issue happening at the time.
Customer: replied 2 years ago.
Expert:  Doug replied 2 years ago.
Yeah that really doesn't look too awful. Lets just give it a cursory wipe down and clean the edge of the throttle plate and recheck operation.
Customer: replied 2 years ago.
It seems pretty clean. Could have a possible air restriction in intake line underneath that weird breather could that do it?
Customer: replied 2 years ago.
I can't move the throttle plate with my fingers easily, is that normal?
Customer: replied 2 years ago.
Also during initial start up the tb clicks and an audible buzz can be heard while in aux and operating gas from interior.
Expert:  Doug replied 2 years ago.
It should move pretty easily... there is spring tension there with the key off, but that is it. You shouldn't have to fight with it.
The noises are not abnormal. With key on engine off it will click 4-5 times (almost a clucking sound) and then continue to hum/buzz indefinitely from that point on. It always does this, you just usually can not hear it over the engine of course.
Customer: replied 2 years ago.
OK, so I guess I move onto this, reassemebeled after wiping took it home 30+ miles and the issue hasn't seemed to return... Will do a second test tomorrow and really warm it up because it sat for a bit. Usually it happens about 1+ hr of driving when coming to a stop. Would a vacuum leak and / or air restriction cause this kind of bucking? The rpms flutter to match the Buck as well. Idk if this helps too, but the idle is like 750 Rpms. It does need an oil sender switch as well. The oil light kind of flickers at idle after being warmed up, sometimes remains lit. Don't know if that helps or plays into the situation.
Expert:  Doug replied 2 years ago.
Let's see how it goes, hopefully we can get by with just that, as otherwise the throttle is very suspect, which odds something you don't want it to be (for both diagnostic and cost reasons).
A vacuum leak can cause a good number of issues, but not really so much like you describe. Most leaks can be found using unlit propane while the engine oodles (it will suck in the excess "fuel" and fluctuate the idle).
Customer: replied 2 years ago.
Alright, I'll give it a more in depth testing. Report back tomorrow afternoon. I ask about the vacuum leak and or air flow from air box because that vacuum line was disconnected and intake connectors were loose before and once adjusted and connected it seemed to do better. Also the intake on my mitsu appears to be off a different mitsu 3.8, maybe Montero. Because it doesn't fit correctly and causes a kink in the top elbow underneath that odd breather thing towards the top of the intake tube. The airflow could still get thru but there is a definite restriction. Was thinking of going aftermarket to increase flow to bring the idle up.
Expert:  Doug replied 2 years ago.
No problem, I will be in late tomorrow afternoon.
If you can get some photos of both your intake and the hoses in detail that might help. If things are wrong there, it may be related.
Stay away from the aftermarket pipe intakes; they make noise, cost you low end torque, and set you up for potential engine damage in heavy wet driving.
Customer: replied 2 years ago.
Was unable to get to it today. Will get oucs poster to u tomorrow morning. I ha e done some research and it looks exactly as it should for a 3.8l engine it just doesn't fit right, ull see in photos. Also, on just a side note. Ur not thinking it could be a transmission with all those miles? Or would that happen despite cold/hot conditions?
Expert:  Doug replied 2 years ago.
No problem at all.
I would not be too suspicious of the transmission. The only thing I could see would be perhaps a solenoid sticking on acceleration or something along those lines... but to do that and -not- have either a shifting problem or a transmission fault (N light flashing) would be extremely unlikely.
Customer: replied 2 years ago.
Update, the car runs better a few stutter or hesitation when warm but only brief. In my research last night I noticed the recommended octane is 91. Could the old owner have out regular in the tank? ( i haven't filled the tank yet) was planning on putting regular due to lack of label on interior gas cap. ( my 3000gt has a label that say premium octane only.) Could this be a potential along with the TB. I know deposits can build up from cheap regular gas.
Expert:  Doug replied 2 years ago.
Hi,
If you run regular octane the engine will perform pretty poorly. From a stop there will be a noticeable delay and often a "cluck" sounds as the timing is retarded and the initial combustion knocks.
Otherwise a lot of people will run regular in this car and the Endeavor, even though they are meant to have premium. Whether or not that is enough to cause your symptoms, that is hard to tell without feeling them myself. That combined with slight build up on the throttle could have caused enough hesitation/etc.
I would definitely run premium only anyway, but running a tank through of quality brand premium at this point will likely be helpful in determining if there is a relation.
Customer: replied 2 years ago.
Will do. Seems to be better though, took it for a long drive and ran into a lot of stop and go traffic. Like I said it did do it once or twice, but didn't act as bad. I will put a few gallons of mjdgrade to check for improvement. If it improves I'll fill with premium. I noticed I forgot to get u the small kink in the airline elbow. Will do his asap.
Customer: replied 2 years ago.
The car did sit for awhile ( unknown time) before I purchased it. Just an FYI.
Expert:  Doug replied 2 years ago.
No problem at all.
The sitting could certainly be relative as well, as fuel does not shelf well anymore... where a decade ago you could let a car sit for 3 years and not worry about the fuel in it, these days it seems like it only takes a few months before the fuel turns and can cause pretty horrible performance (or even no start).
Customer: replied 2 years ago.
Issue is still occurring today. Like before, not as bad but still a good hesitation/buck/cough. Today the TCL turned off. Not sure what that is about. For a period of time the CELs went away. The Cat efficiency code, o2 temp, 02 under flow. After the bucking/chocking occurs they came back on.
Expert:  Doug replied 2 years ago.
Thanks.
Let's get the ABS/TCL fault scanned top see what is going on there... This does steer us toward a potential throttle body issue, as that is about the only engine related component that can set the TCL light on from malfunction, unless it just happens to be coincidental timing... I'm not a big fan of coincidences though.
Customer: replied 2 years ago.
OK great, will that throw a code I can pick up via obd2? Or is there some other means?
Expert:  Doug replied 2 years ago.
It depends on what the fault is and the severity of it. If it is not engine related (like a wheel speed sensor) it won't always set an obd fault. If it is throttle related eventually it will set a throttle fault in the obd system too, but will be in the ABS first.
Also it is possible to only set a generic obd fault (like P1773 etc) for "ABS fault", which of course is not too helpful. Ideally an ABS scan is preferred as it will always offer more detail.
Customer: replied 2 years ago.
The TCL is now off. Will the code still be stored in an ABS scan? I can bring it to a shop around here and see if they have that type of scanner
Expert:  Doug replied 2 years ago.
The ABS faults do not have around as long as the obd faults, but they will retain after the light goes out for a short period (usually a day or more), as long as it was an actual fault (lit solid) and not an activation of the ABS (flashing).
Customer: replied 2 years ago.
Ya it the traction control off light came on solid, was on until I just turned it over to see if there was an obd code. I'll have a shop check tomorrow afternoon for an ABS code of some kind.
Expert:  Doug replied 2 years ago.
Yep, it should have a code stored then.
Customer: replied 2 years ago.
Update: mechanic took a look. Codes are: p0421warmup cat bank 1, p0431 warmup catbank 2, p0102 airflow signal voltage low. TcL and abs codes come tomorrow he didn't have right adapters on him. He seems to lean cats. But they are pretty expensive so I'd like to weigh aftermarket header options to delete cats. Some other helpful stats he said to give u are here: throttle 2.7% @ 700rpms. , map 30kpa.
Expert:  Doug replied 2 years ago.
Thanks. Throttle and pressure readings are okay.
The cat faults should not have too much emphasis put on them... These cars are very common for catalyst faults and pretty much never cause a drivability problem. The Mitsubishi software is extremely critical of catalyst efficiency, and in the extremely rare cases where the catalysts clog and cause issues, those faults have usually been on for 150k+ miles. The efficiency fault just means that the chemical reaction is weak, not that there is a clog or anything like that.
I would be more focused on the 102 fault... I would want to inspect the wiring carefully for any abnormalities (pinched, chaffing, corroded), and if nothing unusual is found I would try a new Mitsubishi MAF.
Customer: replied 2 years ago.
Roger. The old owner said he replaced the MAF. Would it be safe to say this is a common issue?
Customer: replied 2 years ago.
What company does mitsu utilize for this Mac, back/arnley, dorman, spectra, general performance?
Expert:  Doug replied 2 years ago.
Not like it was in the 90s or anything, but I've had a dozen or so come in bad in the past 2-3 years.
It wouldn't be surprising, hows that? :)
As long as there is a P0102 which is literally saying the MAF reading is out of range (the voltage generated is not a plausible value), there really isn't too much else to expect. PCM problems are EXTREMELY rare, wiring problems are not common unless there was a reason like an accident or a rodent in there etc. The only other things that would cause the MAF reading to go out of range would be real long shots (timing belt jumped a few teeth creating unusual air flow, yet somehow NOT causing correlation faults etc).
It is a pretty solid case for a MAF, particularly if it was occurring before and only a used or aftermarket MAF was installed as those aren't really safe to use and assume good.
Mitsubishi does not outsource most of their electronics... which is why aftermarket ones are so common to malfunction or even not work at all right out of the box... they don't share, basically. Mitsubishi MAFs in particular are all in-house, from Mitsubishi Electric.
Customer: replied 2 years ago.
If i HAD to go aftermarket, are there any youwould recommend. a MAF from Mitsubishi is well over 200+$ where tons of dfferent aftermarkets are right aroud 50-75$. Just dont want to replace a part,still have the issue, and be out 200+$ for a new MAF. I only say this knowning the old owner has already swapped tthe MAF off one from a junkyard. What are the chances that both MAFs where bad yaknow? Unless there is a reprogramming that needs to be done to the TB at all w/ a new maf??
Customer: replied 2 years ago.
Would it be safe to say i could confirm the MAF is faulty by disconnecting it and driveing?If the issue with the bucking does not occur then it is likely the MAFs reading?
Expert:  Doug replied 2 years ago.
I would sooner recommend you try a handful of used ones before aftermarket. They are that sketchy. For $50 though, you could always buy one and if things are different but not fixed just keep exchanging it until you get the results you are looking for. I've had customers do that with cam sensors (another problem area for aftermarket parts on these cars) and go through 6-7 exchanges before getting one that works right.
There is no programming for the throttle body; it adjusts every time the key is on and calibrates after three key-ons. It does not store logic on it like VW or Volvo throttles, for example, so there is no programming to it.
Disconnecting the MAF is not conclusive... while in some cases it will cause improvement in others it can worsen things. There is no real pattern to it. Further, on the off chance it were something else it could theoretically still improve things and as such would not tell you anything that way either. When the MAF is unplugged it essentially causes the computer to ignore all sensor input except cam/crank sensors, as the key sensor it uses for comparison is missing.
It is certainly worth a shot, but by no means a rock solid basis for reasoning.
Customer: replied 2 years ago.
Is it typical that the MAF would only be malfunctioning only at low speeds when warmed up? say 0-35ish. The buck problem also only occurs ,as i said before, when it is nice and warmed up. It just seems as though it occurs when it wants to, but you can feather the throttle to get it to act correct. However, once it starts to occur it usually will keep happening until the car has been turned off and sufficiently cooled. If still driven around while the buck is occurring the car will stall when coming to complete stop,will start up and drive a ways and buck/limp along. But I have noticed once I'm 35-40, its smooth sailing not even a hiccup regardless of when and if the problem is occurring. I think for these reasons my mechanic is leading towards the cats being clogged w/180k. But I prefer to have a proper knowledge base in which two heads are better than 1, also he is an old time ford/gm mechanic and has stated the new fly-by-wire isn't his forte. lol
Customer: replied 2 years ago.
We will be pulling a full diag out of the obd/can system to get ahold of those tcl/abs codes regardless, because i know we all were even leaning TB before I got you the full and correct codes yesterday.
Expert:  Doug replied 2 years ago.
The malfunction depends on what is going on with it. If the reading is skewed, then yes. If it were an open circuit or dead shorted, then no it would not behave that way.
Again regarding the cats it is very unlikely.... possible, but unlikely. Either way you can pretty easily compare the flow at the exhaust tip to see if there is restriction or if you have decent flow exiting. Additionally, if it were the cats, unless it was the clean up cat under the car which is not monitored (and I have a feeling the front ones that are monitored throwing faults is the primary basis for that assumption) you would have to have both sides clog at the same time to do this without setting any trouble codes for it (as one side clogging will cause the trims to freak out), and on top of that a clogged cat doesn't typically exhibit this symptom without also having hard-starting problems.
Customer: replied 2 years ago.
Awsome, apprciate the knowledge. Will help to explain it to the mechanic, the flow out the back exhaust is healthy. Will check those CAN/TCL/ABS codes and report back later today. ~5-6pm EST, will try and disconnect MAF and drive it warm. Id assume if the problem does not persist than the MAF would be suspect, just in my laymans eyes. If a host of other issues comes along with the d/c of the MAF I may just drop the 78$ for a beck/arnley who reference the part number w/mitsu's (MR985187). They are a reputable company and can always reach out to thier factory and bugout if it doesnt operate as expected. Before I run out and purchase the MAFthough ill get u the rest of those codes later tonight. Thanks agian for your patience and help in this matter!
Expert:  Doug replied 2 years ago.
Yeah if you have healthy flow out the tail pipe, the cats are likely the wrong tree to be barking up. It can be hard to over look when there are codes like that, but they have to remember that they are efficiency reports, not clog indicators. Another tip regarding clogged cats... if you run the engine at night and rev it up for a a minute or even less, they will usually glow -bright- red from the exhaust not being able to exit.
I'll be in this evening, just drop those codes whenever.
Customer: replied 2 years ago.
Stillwaiting on the TCL and ABS codes, uncle has not been around to do it. I replaced the MAF and notice while doing this the battery connectors and stretched and loose over the terminals. The idle seemed better after the MAF was changed but due to the battery connections having questionable continuity everytime id touch that cable harness the idle would bounce around. i had taken it for a drive and it only did that buck once, would a loose battery cause a bucking/bouncing RPMs only at low speeds? Eitherway I bought new terminals to make solid connections and will get a better MAF test ideally today.
Expert:  Doug replied 2 years ago.
Hi,Thanks for the update, keep me posted.