Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Thank you for using Just Answer for your needs. I see that you cleaned the IAC. How was it cleaned? Removed from the throttle body or cleaned on the car?
Also who has been doing the work? A repair shop?
I left the throttle body on the car - cleaned it with carb cleaner and have been doing most of the work myself with a buddy who is a certified master mechanic.
It is my daughters car and she has had a few shops look at the car and they have made some of the repairs (eng. mount, fuel filter, fuel system 3 step cleaning, timing belt). Me and my buddy are scratching our heads at this point.
I don't think you guys should be as you are close to the problem. We see this problem often and the symptoms you are describing are the pattern. the problem is the IAC itself.
We also recommend cleaning it first but this doesn't always work. I would suggest that you replace it but you can take it off of the throttle body and clean it. This is what it will look like...
That silver door you see is what gets stuck by carbon build up but please remember that these also do go bad and need to be replaced(along with the gasket).
According to your answer, if I replace this then I should have no more problems associated with the ones I explained to you, right?------------ if i replace the IAC and it doesn't fix the problem, what could it be then and can I contact you about it without getting another $18 charge?
Also, is it customary that the gasket comes with the IAC when you order it?
Thanks for the reply and yes it will work. If you ever do need to re contact me, just reply back and I will see it. Also the gasket will come with the new IAC but the throttle body gasket will be separate.
Genchi, I removed the throttle body and Idle Air Control Valve and cleaned them both thoroughly. I replaced all the vacuum lines on the Throttle Body as well. The car runs fantastic, but I am still having the same cold start problem periodically. I am stumped, what's next?
I already paid you ----- I still require your help
What is the specific problem you are having now with the cold start?
The car will start, then the idle revs up to @ 2000 rpms then drops back to @ 650 rpms, then goes back up to @ 2000 rpms and then drops back down abruptly ---- it does this a few times and most often after a couple cycles it will die out completely (stall). Sometimes it will cold start and stay @ 1200 rpms and not act up until you depress the gas pedal once to try and get the idle back to normal (@ 650 rpms).
Once the car is warmed up, it starts and idles/runs perfectly. Sometimes it stalls when going down long inclines without depressing the gas pedal, but only when engine is cold and not often. (Note- I have already cleaned the throttle body and Idle Air Control Valve extensively, replaced all vacuum hoses to throttle body, replaced the fuel pump, fuel filter, fuel pressure regulator, and fuel pump filter). THIS PROBLEM NEVER THROWS A CODE - and it is driving me crazy!
If the idle is varying wildly still then the next step would be to replace the IAC as this is what controls the idle speed.
Let me get another Expert involved with us to get their take.
Have you tried to observe scan tool data while the condition is occurring? Map sensor readings? Injector pulse? IAT and ECT?
This does not sound like a conventional problem and I think we should start by seeing exactly what's going on because the only thing left in the IAC is the wiring and the ecm. You could check the wiring for the IAC to the ecm but let's see the data list and see what's going on when it's happening. You're gonna need a good scan tool that's fast enough to keep up with the erratic condition and if you can record the data to be viewed later would be ideal.
I have checked the car in this fashion and also by connecting a creiger (sp) early on during discovery. The problem throws no codes and all components associated check out fine when checked with an ohms meter (derived from car manual) and by scanning. As a rule, I broadened my search for a possible problem once I felt that I checked/cleaned and replaced most parts that would normally cause this problem without throwing a code. During research I came across the Engine Coolant Temperature Sensor (ECT) and learned its function within the EFI system (which you never mentioned) - although the sensor appeared to be working fine & checked out okay with the meter, I decided to change it anyway. In doing so, I inadvertantly solved my problem myself. By doing this (and also cleaning/replacing the throttle body and IAC valve I am sure did some good as well) the car is running awesome now. Please share my experience with others in the future to possibly save them some time and money with this similar problem.
*Note* I have already paid Mr. Genbutsu early on with his first recommendation (because I thought that was usual and customary even though it did NOT fix my problem) ---- I do not want my money back even though I solved the problem myself, all I ask is that you share this info with the next person with my problem.