Alright, 2000 C2 tip with 110 k miles on it. Daily driver runs very well. Pulling up to a stoplight idle is fine for first ~20 seconds. Then there is a slight stumble, maybe 200 RPM. Comes back smooth for about 10 seconds, then stumble, then recover. Never goes below 600 on the Tach. I have read the posts about cleaning the throttle body. Done that twice, no difference. Attempted to clean down past the TB because I could see a little gunk in the runners. Also cleaned MAF more than one time, no improvement. No codes at all. Has thrown codes but they were fixed and not related. Any other thoughts on this. Car has always done this since I had it (got it with 70k). Have changed plugs, fuel filter about 85k, no difference. I have a durametric scanner but seems like when I feel like running tests I get an error message and it shuts down. New O2 sensors about 10k miles ago.

Dealer said during a training session that it was common if I used gas with ethanol. Prior to the hurricane in Texas last year I always used gas w/o ethanol. Still had the problem when I used that gas. Dealer said they were told to go to mid-grade and not premium as the gas was less affected by ethanol. Two tanks later and still the same problem.

Thoughts on what else to do? Not a big issue but I sure don't want to lead to a stall at a stoplight.

 

check for intake leaks... and vacuum as well.

 

I would say clean the throttle body..but you did that already.
Intake leaks will trigger a CEL...
Try fuel injector cleaner.

Good luck

 

Possibly early symptom of AOS failure?
Did you check the coil packs for hairline cracks?

 

I haven't checked the coil packs, although I did replace the plugs. Probably didn't look that closely though. Is there a way to test them? I did replace the connectors from the coil packs to the plugs. I have been using afuel injector cleaner. I thought about vacuum leaks but I haven't done that kind of work since carborateurs(sp?). Not sure how to check the AOS though. I have heard about opening the oil filler and feeling for vacuum, lack of vacuum bad AOS (do I have that right?).

 

Look for cracked coils or corrosion.
Testing procedure...
Check the resistance across pins 1 and 15 (black wire and green wire w/stripe -- NOT brown).
Resistance should be 0.3 to 0.7 ohms.

They usually last around 60k from what I was told.

If they all look corroded I would replace them all, but if they look and test good just replace the one that test bad.

 

Under the car, at the rear of the motor (behind the driver side rear seat) look at the rubber belows of the aos to see if there are any cracks/holes....