Warm Idle - Random stumble & stall - Similar experience
08-10-2009, 11:31 AM
#1
Race Director
Thread Starter
Warm Idle - Random stumble & stall - Similar experience
Guys,
Looking for some advice/experience so i don't need though parts at this issue.
My car has a warm idle sumble. What happen is that I can start the car and it runs fine. Cold idle is good. It does idle about 100 rpm high, but nice and smooth. (88 motor, 88 controls, stock DME chip)
So I take it out on track and run it when I pull in it still idles at about 1000 rpm. However if I let it idle for 5 minutes it will occasionaly stumble and stall.
Next session of the day I pull pu on grid with a warm, but not fully up to temp motor and it occasionaly stumbles at ldle again. If I give it gas I can get it to recover some times. Most of the time it will restart, but on occasion it will crank, but not fire. Wait 1-2 minutes and it comes back.
On track at full throttle the car run perfect with no misses and full power.
I am thinking it is an electrical issue since it can work fine and then just die for no reason. DME temp sensor seems to be fine, but I have never measured temps when it stumbles. AFM is working fine too. I have replaced the O2 sensor with no effect and even run without the O2 will no effect. (remember this a non-street legal track car with no cat).
TPS has been checked. So anyone else have warm idle random stumble?
Looking for some advice/experience so i don't need though parts at this issue.
My car has a warm idle sumble. What happen is that I can start the car and it runs fine. Cold idle is good. It does idle about 100 rpm high, but nice and smooth. (88 motor, 88 controls, stock DME chip)
So I take it out on track and run it when I pull in it still idles at about 1000 rpm. However if I let it idle for 5 minutes it will occasionaly stumble and stall.
Next session of the day I pull pu on grid with a warm, but not fully up to temp motor and it occasionaly stumbles at ldle again. If I give it gas I can get it to recover some times. Most of the time it will restart, but on occasion it will crank, but not fire. Wait 1-2 minutes and it comes back.
On track at full throttle the car run perfect with no misses and full power.
I am thinking it is an electrical issue since it can work fine and then just die for no reason. DME temp sensor seems to be fine, but I have never measured temps when it stumbles. AFM is working fine too. I have replaced the O2 sensor with no effect and even run without the O2 will no effect. (remember this a non-street legal track car with no cat).
TPS has been checked. So anyone else have warm idle random stumble?
08-22-2009, 01:20 AM
#3
Race Director
Thread Starter
Did some diagnostic testing today.
Swapped DME and DME relay. No change. I did only Idle testing.
Anyway warm the car will idle just fine then drop idle then come back. I did alot of contact cleaning today and there were no stalls just the same issue.
Also of note is the at DME relay clicks when the idle stumbles. I swapped relays and it did the same thing so I don't believe the issue is in the Relay and the swap DME rules out a bad DME.
No driveablilty issues on track under power. Only at idle.
I have replaced the O2, but maybe it is bad?
Swapped DME and DME relay. No change. I did only Idle testing.
Anyway warm the car will idle just fine then drop idle then come back. I did alot of contact cleaning today and there were no stalls just the same issue.
Also of note is the at DME relay clicks when the idle stumbles. I swapped relays and it did the same thing so I don't believe the issue is in the Relay and the swap DME rules out a bad DME.
No driveablilty issues on track under power. Only at idle.
I have replaced the O2, but maybe it is bad?
08-22-2009, 01:36 AM
#4
Nordschleife Master
unplug it and see if the stumble at idle changes... if no change get a new O2... if there is a change clean your ISV, or delete it...
My bet is O2 sensor...where are you getting fuel? some tracks still pump leaded and it will KILL O2 sensors dead..fast
My bet is O2 sensor...where are you getting fuel? some tracks still pump leaded and it will KILL O2 sensors dead..fast
08-22-2009, 03:36 AM
#5
Race Director
Thread Starter
I run 91 pump gas only. Too cheap for race gas.
When I un plug it does not really change. Slightly, That is why I am thinking bad O2. However that should not cause a stall. I have run with no O2 before.
When I un plug it does not really change. Slightly, That is why I am thinking bad O2. However that should not cause a stall. I have run with no O2 before.
08-23-2009, 03:19 PM
#6
Racer
Join Date: Nov 2006
Location: Arvada, CO
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A disconnected O2 sensor will cause it to run pig rich (or at least it does here in Colorado; I failed emissions spectacularly when that happened), but if it were just broken and giving a false rich signal, it's possible that the DME would lean the mixture out too much.
