Slight stumble at idle, thoughts

[GranburyChuck]

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.

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

[function12]

I would look here.

http://www.renntech.org/forums/index.php?showtopic=6828

[GranburyChuck]

I would look here.

http://www.renntech.org/forums/index.php?showtopic=6828

Thanks, but that is for a '99 (non e-gas) car. Mine is e-gas so I don't have one.

[Loren]

Clean the throttle body.

[win911]

Also, put some fuel injector cleaner in your fuel tank... I use Techron fuel injector cleaner at every oil change.

[bmohr]

possibly coil paks? Can you have a loss of perforamce without throwing codes with cracking/failing coil paks?

[GranburyChuck]

Well, I have cleaned the throttle body multiple times. Last time, about 3000 miles ago, it looked essentially spotless. No dirt on the rag. I have used Techron and other cleaners, no difference there. When I replaced the plugs I changed out the connectors from the coil packs to the plugs. I don't recall looking very closely at the coil packs though. I wonder if there is a way to test those?

[Loren]

Well, I have cleaned the throttle body multiple times. Last time, about 3000 miles ago, it looked essentially spotless. No dirt on the rag. I have used Techron and other cleaners, no difference there. When I replaced the plugs I changed out the connectors from the coil packs to the plugs. I don't recall looking very closely at the coil packs though. I wonder if there is a way to test those?

If you had a coil pack problem you would have misfires and a a CEL.

Time to look more closely at the possibility of air leaks.

[td873]

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.

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

How long has this been happening? And when was the last time you filled up with gas?

-td

[GranburyChuck]

This has been happening about 1.5 years. I have gone through many variations of gas especially after the hurricanes hit Texas. Porsche dealer told me to drop down to mid-grade because of less ethanol impact. Didn't seem to matter.