[Gmecm] creepy idle

[Andrew Gibson]

I just had a really weird thought today. If it's not doing it in reverse, but is in drive, and the IAC is climbing as high as you say it is, It's definitely not in the sensors or IAC. Steve you said it will reach 2000 rpm if put in neutral. That means the IAC is flowing enough air. And reverse will require more engine load (reverse pressure boost on the trans pump) so it should cause more problems if it was engine management.
   
  I'm still thinking something with the trans as before. Only this time in the TCC. If I remember right (I don't have the hydraulic diagrams of the 700r4 at home) the tcc is completely diabled in reverse. Park and Neutral it doesn't matter. But if it is staying partially on in drive you will have a problem with increased load. You may want to check the brake switch, tcc pressure switches in the trans and the tcc soleniod itself. A more rare possibility is cross leakage in the pump or valve body.
   
  As for the scan tool. If the ecm sees a glitch it will substitute limp in values in the datastream to get you home (The O2 bais voltage is a good example.) Also unless the scan tool, your eyes and the ecm are fast enough you will never see a glitch or dirty signal. Especially from a bad distributor shaft. However unless the engine runs like absolute crap (typically a random misfire) and smooths out to run great with the est bypass disconnected, I wouldn't worry about a bad distributor shaft.

			
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