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ChevyTech · 08-04-2018, 10:48 PM

With an IAC count of 145 to 150 it should have a very fast idle. It should not be slow and loping.

The PCM sends out pulses for the IAC to open as the count is going up to 150. The PCM does not know what the real position of the IAC is it just tracks the pulses sent out to it.

Make sure the IAC passage is not blocked with muck and build up. It kinda sounds like that is the problem. The IAC may be moving but there is no increase in air getting though it.

Maybe the wrong IAC is in it. The pintles have different shapes on some of them.

08-04-2018, 10:48 PM	#11
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,620	Re: Rough idle in closed loop With an IAC count of 145 to 150 it should have a very fast idle. It should not be slow and loping. The PCM sends out pulses for the IAC to open as the count is going up to 150. The PCM does not know what the real position of the IAC is it just tracks the pulses sent out to it. Make sure the IAC passage is not blocked with muck and build up. It kinda sounds like that is the problem. The IAC may be moving but there is no increase in air getting though it. Maybe the wrong IAC is in it. The pintles have different shapes on some of them. __________________ For those of you that are wondering why you are not getting replies to your thread: Did you give the model, year, engine, fuel system type, and transmission information? If it is modified from what came stock from the factory, let us know that too.