Toyota Repair: Camry stalls after warming up to operating temp., vacuum leaks, vacuum gauge

Question
Ted,

My '93 Camry with the 3VFE 3.0 V6 is still not holding an idle.  The problem seems to have gotten worse, in that now it never holds an idle, where before the problem came and went and seemed to be linked to hot or cold engines.  Now it just won't idle ever, but it still runs smoothly if you manually hold the idle at 750 RPM.  And it runs smoothly throughout the RPM range of normal driving.

Since I lasted talked with you, I had a local mechanic check the car for vaccuum leaks, and none were found.  He also found no trouble codes in the computer.  He suggested as you did that the IAC was probably still the culprit, even though I had cleaned it.  

I replaced the IAC valve, but nothing has changed.  The car still will not idle.

Do you have any other ideas?

Thank you for all your help.

Roger Strew


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Followup To
Question -
Follow Up Question---Original question at bottom of page-----

Ted,

Thanks for such a quick response on my question about the '93 Camry 3VFE V6 stalling problem.

I checked the hoses and vacuum lines for visible signs of cracks, looseness, etc., and found nothing.  I don't have a vacuum gauge, and I'll admit checking for vacuum leaks with a gauge is beyond my comfort zone.  

I do have a follow up question though.  As a novice I have a hard time understanding how a vacuum leak would only show up at certain times, like after the car is up to normal operating temp?  In my simple understanding, I'd think a leak would always be present, and always make the car run rough?

I made another test run in the car tonight before putting it outside, and now think the problem is completely intermittent.  Yesterday, as I reported to you, after cleaning the IAC valve the car ran smooth during warm-up and began stalling out at traffic lights after it was up to normal operating temp.  Tonight, I just did a test loop in the neighborhood, and it ran rough when it was cold.  At a stop sign with the car in drive, the idle would drop down to 500 RPM and run rough.  I noticed if I turned the wheel enough, the drag from the power steering pump would force the engine idle to jump up to 750 again and run smooth.  After several laps through the neighborhood, the temperature finally reached normal, and it began to stall at stop signs just as before.  I drove with two feet back to my house, but when I put the car in park, it did not die, it just started to smoothly idle at 750 RPM.  This made me wonder if the problem only occurred when the car was in gear, so I shifted back into drive, and the idle held steady at a smooth 750 RPM.  So, I took another loop or two around the neighborhood, and the car ran perfect at normal operating temp.  It idled at a smooth 750 RPM at every stop sign.  I took it up and down some very steep hills to see if lugging up a hill would cause a stall, and it did not.  And conversely, coasting down a hill didn't kill it either, as it had before.  The car ran perfect.

Given the intermittent nature of the problem, do these symptoms point more directly at a particular problem?  

I really appreciate your advice.  Having seen how kind people like you are helping so many on this site, I wish I was an expert in something so that I could help others and give back as you are.  Thank you very much.   


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Followup To
Question -
Ted,

I have a '93 Camry with the 3VFE 3.0 V6.  It will not idle after coming up to operating temperature.  From reading your past advice, I removed and cleaned the IAC valve.  It was pretty fouled, so suspected it was the culprit.  After a long test drive including highway speeds, stopping at a red light would cause it stall again.  But during cold start up the car performed well, and idled at about 1100 rpm.  I jumpered the TE1 and E1 diagnostic ports, and got only the normal mode, continuous flashing light.  Do you have any further advice?  I appreciate any help you can give me.  This is a great site because of the many helpful people on here like you.  Thanks again.
Answer -
Since there is no check engine light the problem is mechanical and not related to the EFI system with the exeption of a faulty air flow meter which in most cases will not trigger a check engine light, but before replacing this expensive part you need to check for any air leaks on the intake side, check for any loosenes or cracks in the large intake hoses from the air filter to the throttle body also check for any other possible vacuum leaks on the intake system.
Answer -
Theoretically, an intake air leak may not cause a problem on cold starts because the computer richens the air fuel mixture and increases the idle speed like it is supposed to, at higher engine speeds around 1500 rpm an air leak will have little effect on the idle but when the engine returns to normal idle speed after warm up the correct air fuel mixture becomes much more critical.
The only other advice I have at this time is that maybe cleaning the IAC valve did not fix the problem and it may have to be replaced.

Answer
The only other thing I can think of is that there may be a misfire at idle that is intermittent, this could be caused by possibly a bad coil or worn spark plugs or plug wires or possibly a distributor rotor, sorry, can't come up with any other logical solution at this time.