Stumbles / Hunts / Low (500 RPM) Idle
01-17-2008, 11:44 PM
#1
Stumbles / Hunts / Low (500 RPM) Idle ALL -
My LT1 is now giving me a new issue to address - mainly when it it cold. It stumbles and has a very low idle speed (500 RPM). Sometimes it hunts and finds its old idle (950) and at other times cycles between the two speeds; sometimes resting at 700 RPM or so too.
I think it's the Idle air stepper (IAC) motor in the TB, which is only about 18 months old, but my step-father (a master mechanic) suggested it might be a coolant temp sensor as well (also 18 months old). He suggested the ECT might be reading HOT, causing the PCM to reduce the fuel sent to the cylinders, then when the engine does warm up (to the temp the ECT says it is), then the problem goes away because the amount of fuel sent to the cylinders is indeed correct. That's his logic / speculation anyway...
Any suggestions on other possible root causes?
MIKE
My LT1 is now giving me a new issue to address - mainly when it it cold. It stumbles and has a very low idle speed (500 RPM). Sometimes it hunts and finds its old idle (950) and at other times cycles between the two speeds; sometimes resting at 700 RPM or so too.
I think it's the Idle air stepper (IAC) motor in the TB, which is only about 18 months old, but my step-father (a master mechanic) suggested it might be a coolant temp sensor as well (also 18 months old). He suggested the ECT might be reading HOT, causing the PCM to reduce the fuel sent to the cylinders, then when the engine does warm up (to the temp the ECT says it is), then the problem goes away because the amount of fuel sent to the cylinders is indeed correct. That's his logic / speculation anyway...
Any suggestions on other possible root causes?
MIKE
