Would that also cause the vehicle to hesitate when first started? I
notice this more as the temp gets lower. I just start it and put it in
gear and when I push on the gas, it will hesitate. Sometimes it
backfires. Sometimes the engine even dies. Once going though, there is
Not really... the sole purpose of the IAC motor is to allow the engine to
get enough air when the throttle plates are closed (foot off the
accelerator) to maintain proper idle speed. If the engine's idling fine,
the IAC is working properly. It could be a bad TPS (throttle position
sensor), who's job is to monitor the position of the throttle plates. The
PCM uses this to say, "Ah hah, the throttle plates are opening, so I need to
add more fuel, adjust the timing, all that fuel-injection stuff". The PCM
uses the TPS reading as sort of an "early warning" that the mixture's going
to go lean, rather than wait to sense a change in pressure within the
manifold (via the MAP sensor).
Try this next time... put it in gear, give it a couple of seconds, then let
off the brake, but don't give it any throttle. If the engine is still
running smooth, VERY gently and VERY slowly apply some throttle. If that
keeps the engine running good, but nailing the throttle from a stand-still
causes it to hesitate, then I'd go ahead and troubleshoot the TPS with a
voltmeter, and if found to be bad, replace it.
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