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Toyota Service
Toyota Service, Lexus and Toyota expert
Category: Lexus
Satisfied Customers: 4538
Experience:  30 + years of experience; Multiple Award Winning Svc Mgr; Just Answer Customer's Choice Award Winner
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I need a clever, intelligent Lexus/Toyota technician with

Customer Question

Hello,I need a clever, intelligent Lexus/Toyota technician with access to Techstream to help diagnose an engine issue with my 2001 Lexus LS430. I have an ongoing issue that has stumped three mechanics using three different computerized engine diagnostic platforms. I, with Techstream, am included among the three. I am not a professional mechanic, but am very adept and both have and follow the factory service manuals. Therefore I have a recording of all sensor and monitor data with flags I added every time the engine seemed to misfire as well as a video that I will upload or send to him or her.On cold start, the RPM jumps to about 1,500 initially, drops to about 1,000, shakes the car for a few seconds, and promptly jumps back to 1,500. When hot, the car will seem to misfire most noticeably at stops in gear, but also idling in park and under part throttle cruising. There seems to be no predictability or pattern to it, and no codes or MIL are being recorded or triggered. The engine will sometimes seem to shake slightly, resemble a misfire, and the RPM will drop and immediately jump up before settling back to about 750.The car has 135K miles currently, and is well maintained. I am the second owner and acquired it at 117K, two years ago. Full tune up of serviceable items has been done, along with timing belt and ancillary components, off-car ASNU ultrasonic fuel injector service, new fuel pump resistor, cleaned throttle body and IAC port, and complete disassembly, cleaning, and reassembly of intake manifold during fuel injector service downtime. Have used Techstream to reset the ECU as well as traditional battery disconnect with a door open to drain residual charge to no avail. Seriously need to get to the bottom of this issue and correct as soon as possible. Thank you in advance!
Submitted: 22 days ago.
Category: Lexus
Expert:  Toyota Service replied 22 days ago.

Hello. Welcome to Just Answer. Please allow me to assist you. Please allow me to ask a few questions to better identify the problem. First, you mention a full tune up. Please specify the brand and type of spark plugs that were installed, and, what type of air filter is in it (factory, parts store or specialty)? Thanks

Customer: replied 22 days ago.
Thank for the response. I put Denso Iridium plugs in it and use a micro-guard paper filter from the parts store. Also, I replaced the MAF sensor with a new factory unit three months ago.
Customer: replied 21 days ago.
Video added of skipping at idle in park.
Expert:  Toyota Service replied 21 days ago.
I am currently at work. I will review your video and get back to you later today. Please clarify that you have no check engine light on, and no pending or history DTCs. Thanks.
Customer: replied 21 days ago.
Verified no MIL or pending DTC's.
Expert:  Toyota Service replied 21 days ago.

Hmm. The video does not seem to indicate anything; I cannot hear any sound either. Let me ask you this: Does it ever stall at idle when the engine is warm?

Customer: replied 21 days ago.
The video isn't very good because Just Answer limits the file size to 5mb, but if you look at the 15 and 22 second marks you can see the tach needle dip and jump around at idle. So far it has not died yet, but it has come close I think while sitting at a stop light once. If you have any problems viewing the video, I will try to reconvert and shrink the original to upload again or I can provide it to you via email.
Expert:  Toyota Service replied 21 days ago.

I think you have a problem that no scanner on this planet is going to find.

Expert:  Toyota Service replied 21 days ago.

Since you have no codes, you do not have an electrical or sensor related issue

Expert:  Toyota Service replied 21 days ago.

With that being said, the issue HAS to be mechanical

Expert:  Toyota Service replied 21 days ago.

Now...with 135,000 miles on this engine, and based on your excellent explanation of the issue, I am inclined to think that your Acoustic Induction system is the cause.

Expert:  Toyota Service replied 21 days ago.

The acoustic induction system ("AIC") is basically a vacuum-operated mechanical device. The AIC is built into the intake manifold. At idle, the AIC assumes a normal posture. When the engine accelerates, the AIC plate moves. This changes the distance that the intake air has to travel. Sort of like a flap valve, but it changes the length of the induction. If the AIC is sticking, you get exactly what you describe. The AIC, if stuck in the wrong position, will compromise the idle and give you misfire-type issues....but it is not a misfire, so there is no P0300 and related misfire codes. I would recommend 3 or 4 induction cleaning services be performed on the intake manifold. If it is gummed up with combustion deposits, (very common after 100, 000 miles), the induction cleaning is going to clean that gummy stuff out. That is exactly what I would be doing next if this car was in my shop.

Customer: replied 21 days ago.
I thoroughly cleaned the intake manifold while I had it off the car during the ASNU injector service. Here are some pictures. The arm for the AICS actuator did seem to slide less than smoothly as it enters the vacuum modulator, but I used some fine grit wet sanding paper on it and a drop of oil on it and ensured that all worked smoothly before I reinstalled the manifold assembly. Is there a way to test that this is the issue?
Expert:  Toyota Service replied 21 days ago.

(a) Remove V−bank cover.
(b) Remove the air cleaner and intake air connector.
(c) Disconnect the throttle body from the intake manifold
(d) Remove the intake manifold
(e) Using a 3−way connector, connect vacuum gauge to the
actuator hose.
(f) Reinstall the intake manifold.
(g) Reconnect the throttle body.
(h) Start the engine.
(i) While the engine is idling, check that the vacuum gauge
needle momentarily fluctuates up to approx. 39.9 kPa
(300 mm Hg, 11.8 in.Hg). (The actuator rod is pulled out.)
(j) Rapidly depress the accelerator pedal to fully open position
and check that the vacuum gauge needle points to
0 kPa (0 mm Hg, 0 in.Hg). (The actuator rod is returned.)
(k) Disconnect the throttle body.
(l) Remove the intake manifold.
(m) Remove the vacuum gauge, and connect the vacuum
hose to the actuator.
(n) Reinstall the intake manifold.
(o) Reconnect the throttle body.
(p) Reinstall the intake air connector and air cleaner inlet.
(q) Reinstall V−bank cover.

Expert:  Toyota Service replied 21 days ago.

One question, before taking the intake off...Has this vehicle ever been in a frontal collision>?

Customer: replied 21 days ago.
As far as I can tell it is all original. In checking the VIN stickers on the body panels and bumper covers a while back, the condition of all the paint, plus the carfax history all seem to indicate it is original. I think there's a way to connect my vacuum gauge inline with the actuator line with the manifold on the car, but in any event I cannot begin to try until Sunday. I remember being able to manually operate the VVT oil control valves via techstream; is it possible to operate the AICS VSV via techstream also?
Expert:  Toyota Service replied 21 days ago.

AIC issues are uncommon, but they do occur, I cannot say that I have ever needed to see if the AIC system was able to be manipulated by the scan tool. You could disconnect the vacuum from the storage tank and plug it off; see how it idles then.

Customer: replied 21 days ago.
Thanks, ***** ***** give your suggestions a try this weekend and get back with you. Thank you again for all your help so far. If you have any other suggestions between now and then, please send me a message.
Customer: replied 21 days ago.
Were you able to view the new video and the pictures I uploaded about an hour ago?
Expert:  Toyota Service replied 21 days ago.

yes. Missed that but just viewed it. That almost resembles a car we had several years ago. After a LOT of diagnosis and frustration, I found that the crank angle sensor tone ring was cracked. You might want to check that first.

Customer: replied 21 days ago.
How odd. That is the toothed ring on the crankshaft behind the timing cover and the harmonic balancer, isn't it?
Expert:  Toyota Service replied 21 days ago.

Yes. If it is cracked the computer gets the wrong count information. Common to happen on frontal collisions or heavy handed repair procedures in this area. Additionally, if the thrust bearings on the crankshaft are worn, this allows the cranks to walk backward in the block. This could cause the tone ring to move away from the sensor. Worth checking the longitudinal movement of the crank while you have the timing cover off.

Expert:  Toyota Service replied 21 days ago.

Note that this condition (cracked tone ring) will NOT set a code. As long as the sensor is working to some degree, does not have an open or a short in it, there will be no code.

Customer: replied 21 days ago.
One thing I should mention, whether or not it is applicable, is that the timing belt was original. I have replaced the belt et al. on my LS400 about four times over the years so I am no stranger to the process. Being the two blocks are basically the same, the manual for the 2001 states two ways to dial in the cams and crank to install a new belt: either line the dots on the cams and crank to 0 TDC, or align to the alternative marks if balancing on the cam lobes proves difficult. Before I took the old one off, I checked multiple times, and the cams would align to the TDC marks, but the crank would be on the 15 degree mark with the timing cover installed. I have pictures of this as well. The car ran fine this way. However, I set everything back to 0 TDC as per the factory service manual and have been driving it this way for almost 20K miles. What is the reason it was set this way from the factory? Could the ECU be flashed for this timing curve, and could be responsible for the idle issue?
Expert:  Toyota Service replied 21 days ago.

Rereading the timing belt installation (just to be certain); I do not see any recommended 'secondary way' from Lexus. No mention of ECU reflash, etc...However....this also reminds me of another car that was rather weird. It turned out that the tensions was weak and allowing the belt to slack. If you are going to take the timing cover off to look at the tone ring, it would be a very good idea to replace the tensioner whilst you are there. Just to be sure.

Customer: replied 21 days ago.
Here is the page from the manual. There are TDC dots and marks on the cams and backing plates and "T" marks on the backing plates. If I understand the manual correctly, setting the cams to the "T" marks and the crank notch to align with the idler pulley bolt would set them all to approximately 50 degrees ATDC and speed up the repair process because the cams have a tendency to jump off when balanced at TDC on their lobes during reassembly. Like I stated earlier, I'm a deft hand at doing these timing services, so I was able to balance the cams on TDC, not the "T" marks, and the crank dots aligned to zero. Here are pictures of how it was originally. As you can see, having the cam marks on the pulleys and backing plates to TDC, the crank would be at 15 degrees BTDC. It was very odd and I have never had an explanation. The only thing I was able to find was anecdotal on a Miata forum where modders would set their engines this way to increase low-end torque while sacrificing top-end power, but I cannot understand why it came from the factory this way unless it was ordered that way as a dealer demo unit...
Customer: replied 21 days ago.
In any event, I aligned all the marks and dots to zero, lined up the lines on the new belt to match, and after turning it over by hand a few times, put it all back together and have been driving it like this for nearly 20K miles. Unless I misunderstand something in the process, it would seem that the timing was set in a manner inconsistent with the manual. Am I correct in my assessment?
Customer: replied 21 days ago.
I'll recheck it all when I get it all apart. I would think I would have bigger problems if it was misaligned.
Customer: replied 20 days ago.
You know, looking back on the timing belt change... It was another tech on JustAnswer that told me the two ways to set it, reason being the cams tend to jump off their lobes and all. I had uploaded the pictures to him and he advised me how to set it and during the reinstall I got a call that my grandmother who I had been caring for had just died so I was rushing to put it back together and get back home, out of state. I very likely could have set it wrong in haste, and like having a belt jump a tooth (although in this case it would be both cams out of time with the crank, if so) it would explain it. I will pick up a new belt just in case I need to reset it all, take it apart, check how it is set, and get back with you. If all goes well I should be able to do this day after tomorrow. Thanks for all the help so far!
Expert:  Toyota Service replied 20 days ago.

If the belt is stretched, or installed wrong, or too slack, you get computer data resets. The cam position vs the crank position should be as close to a perfect correlation as possible. If not, yes, you can get engine performance issues.

Customer: replied 18 days ago.
Hello, just giving you an update. I had some setbacks this weekend and cannot finish the diagnostics until Wednesday afternoon, so I don't yet have results for your suggestions. I will update you on Wednesday when I am able to finish taking the intake off for the AICS and to double-check the timing, so just hang in there a bit longer, please. Thanks again
Expert:  Toyota Service replied 17 days ago.

Ok. Thanks!

Customer: replied 13 days ago.
Okay, the mechanic and I who replaced the belt and sundry parts determined that in our haste we did not precisely follow the service manual's directions and the timing is slightly off. I am ordering a new factory replacement belt and we will redo the installation next weekend following the manual and will let you know if this fixes the problem. Thank you very much once again for all your assistance so far!
Expert:  Toyota Service replied 13 days ago.

Thank you for the update. I was suspicious that the belt was on incorrectly, but I had no way to be certain. Timing belts installations are precise. There is only one way to get it right; there are no secondary or alternate ways to install it properly. It is either on correctly or it is on incorrectly. I believe that when they line everything up properly your problem will be resolved.

Customer: replied 5 days ago.
Well, the timing belt looks like it might have improper tension because it is bowed inward slightly on the toothed side. The timing marks are almost perfectly aligned at crank and cams, but 'almost' probably isn't properly set -- the right cam is aligned slightly before center with the mark on the backing plate, the left cam pulley mark is centered, and the crank is set at TDC. We have a new Lexus belt, and intend to follow the installation directions of the FSM this time because looking at it it looks like we didn't manipulate the cams to put tension on the belt, we just lined up all the marks to TDC and hung the belt as we have done to my 1UZ-FE. I guess we need to know if it is absolutely necessary to have and use the SST on the cams to set tension? Also, why does the FSM state on EM-19, step 18 to remove the cam pulleys only to reinstall them on EM-24 step 13? I mean, they're keyed and only go on one way, aren't they? So why remove them at all? The manual doesn't seem to say. If you wouldn't mind giving us a bit of clarification, please, and any tips or tricks you might suggest would be greatly appreciated. Thanks again for all your help!
Expert:  Toyota Service replied 4 days ago.

The recommendation to remove the pulleys would only be necessary if you were replacing them too. No need to remove them as far as I know; we dont take them off. The SST is nice because it provides substantial leverage.

Customer: replied 3 days ago.
I'm ordering the SST used, hope to have it by this weekend. I will plan on following the FSM with the exception of removing the cam pulleys. I thought that was strange. I'll report back as soon as we resume work. Thanks!
Expert:  Toyota Service replied 3 days ago.


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