Stumbling idle

Alright guys I've had to put a halt to my own car because I've come across some kind of mechanical issue. My cars been running good for a couple of months, but started having an odd issue I can't seem to figure out. When I cold start it it'll fire right up but after idling for a minute or two the Rpms will drop to where the car almost dies and then catches itself and continues to run, but sounds like it's stumbling and sounds like it has a misfire. The issue is only at idle and normal driving seems like there's nothing wrong at all. In the logs its wanting me to pull out 10% or so of fuel, but only at idle. If i take out the 10% and do another log it wants me to take another 10% out and will continue like this no matter how many times i do it. Any ideas on what could be the problem? I'm at work now but when I get home later today I can post up a tune file and hopefully I still have one of those logs saved if that'll help. Thanks in advance guys.

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Originally Posted by Scottgt21

Alright guys I've had to put a halt to my own car because I've come across some kind of mechanical issue. My cars been running good for a couple of months, but started having an odd issue I can't seem to figure out. When I cold start it it'll fire right up but after idling for a minute or two the Rpms will drop to where the car almost dies and then catches itself and continues to run, but sounds like it's stumbling and sounds like it has a misfire. The issue is only at idle and normal driving seems like there's nothing wrong at all. In the logs its wanting me to pull out 10% or so of fuel, but only at idle. If i take out the 10% and do another log it wants me to take another 10% out and will continue like this no matter how many times i do it. Any ideas on what could be the problem? I'm at work now but when I get home later today I can post up a tune file and hopefully I still have one of those logs saved if that'll help. Thanks in advance guys.

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Check you o2 sensors. Might have a lazy one not giving a signal and the car going rich make it stumble. Run it in open loop and see how it is. How are the o2s reading on start up and idle?

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Originally Posted by Camaro6

Check you o2 sensors. Might have a lazy one not giving a signal and the car going rich make it stumble. Run it in open loop and see how it is. How are the o2s reading on start up and idle?

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O2 sensors seem to be reading about how they always have. I'm just getting ready to head into work now, but I'll take a cold start log and post it up in about 12 hours lol

Attachment 92437 Forgot to log it from a cold start but here's a log of my car just idling. O2 sensors seem to be oscillating correctly but maybe you guys can catch something that I'm missing.

Well I haven't had a lot of time to work on the car, but I've checked little things here and there. I've cleaned the MAF, done a compression and leak down test, tried to check the coils but wasn't all that successful in knowing exactly how. The plugs and wires were replaced and I did a smoke test to check for both vacuum and exhaust leaks which there were none. I'm about out of ideas but I was gonna pull the injectors today to check for leaks. Any other ideas on where to look would be greatly appreciated. I've attached a current tune file if you guys feel like taking a look. Thanks in advance.

I noticed that at zero airflow, your MAF sensor calibration is showing frequency. I believe at zero airflow there should be zero frequency. I wonder if maybe the fuel curve at idle may be a little high.

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Originally Posted by Mbrowning

I noticed that at zero airflow, your MAF sensor calibration is showing frequency. I believe at zero airflow there should be zero frequency. I wonder if maybe the fuel curve at idle may be a little high.

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I kind of have my doubts about that. The zero airflow frequency is as factory and the car was running good for a couple of months before I started having my idle issues. I'll try it just to see what happens though.