Cold start: idle problems, Warm start: runs fine
02-06-2012, 11:31 AM
#1
Cold start: idle problems, Warm start: runs fine Still been slowly but surely tweaking the idle settings in my tune, added some more base airflow and it's getting much better. But there is a strange thing I'm noticing:
1) If it's cold weather, I can start the car and it will fire and idle at my commanded RPMs until it gets to operating temp. If I try to drive it, it commonly will have some surging and pissy behavior. I can drive it 10 miles across town at 198* coolant temp and it won't stop.
2) If it dies and I restart it or if I kill it and restart it in under 30 seconds or so, it still runs poorly. However...
3) If I let it warm close to operating temp and then turn the car off (either in the driveway or once I get to a destination) for at least 30 seconds or so, when I restart it the car will run nearly flawlessly.
It can even sit and cool off for over 2 hours in 20-30* air temps and once restarted will idle at the high rpm I have set for colder coolant temps, then settle where it belongs and drive fine.
I first started suspecting this when I would get fed up with it and turn it off to go adjust the idle set screw. I noticed I could adjust it one day and it would then run, but the next day would go back to surging (and then would idle high due to my adjustment). I started to suspect it might be the length of time it took me to pull hood pins, pop the hood, adjust the screw, and restart the car.
So the last couple times its been running poorly I have let it warm up, driven it (with it never clearing up), then pull over and turn it off then back on and it gets much better.
So my question is, what does the pcm see and reference differently between a dead cold start and a warm/hot/semi cold start? Is there a good reason for this behavior or am I or my car just crazy? Is there a short term memory that could bleed power and forget and have to relearn and be reset? (I don't think there is)
1) If it's cold weather, I can start the car and it will fire and idle at my commanded RPMs until it gets to operating temp. If I try to drive it, it commonly will have some surging and pissy behavior. I can drive it 10 miles across town at 198* coolant temp and it won't stop.
2) If it dies and I restart it or if I kill it and restart it in under 30 seconds or so, it still runs poorly. However...
3) If I let it warm close to operating temp and then turn the car off (either in the driveway or once I get to a destination) for at least 30 seconds or so, when I restart it the car will run nearly flawlessly.
It can even sit and cool off for over 2 hours in 20-30* air temps and once restarted will idle at the high rpm I have set for colder coolant temps, then settle where it belongs and drive fine.
I first started suspecting this when I would get fed up with it and turn it off to go adjust the idle set screw. I noticed I could adjust it one day and it would then run, but the next day would go back to surging (and then would idle high due to my adjustment). I started to suspect it might be the length of time it took me to pull hood pins, pop the hood, adjust the screw, and restart the car.
So the last couple times its been running poorly I have let it warm up, driven it (with it never clearing up), then pull over and turn it off then back on and it gets much better.
So my question is, what does the pcm see and reference differently between a dead cold start and a warm/hot/semi cold start? Is there a good reason for this behavior or am I or my car just crazy? Is there a short term memory that could bleed power and forget and have to relearn and be reset? (I don't think there is)
02-07-2012, 12:49 PM
#2
I'm interested to hear responses to this as well. My car has the exact same thing happening. Very frustrating because the pcm is commanding different air flow values after a warm restart as opposed to cold start and letting warm up fully.
