Rough Idle when in Gear

[Irishdad]

Hi, can anyone help solve my problem with a rough idle when Automatic in gear. Not under load smooth idle. Vaccum is great 20 inch. I have replace EGR, PCV, check TAC, complete ignition tune up to included coil. I know EEF in not working. Appears to be the TVS because when vaccum applied closes. Vaccum lines seem okay. Please help me out. First GM product. Have classic mustangs but could not pass up opportunity to get the 81 vette. Sure has been a headache. One more point. When driven above 1200 runs smooths. good power. Thanks for reading this plea.

 

[Tom Bryant]

It could be the memory in the ECM. It is basically still remembering all of the adjustments it has tried to make to compensate for the worn tune up parts or bad EGR ect. After a tune up or repair of any drivability problem disconnect the battery for about 15 minutes or so. This eraces the settings in the ECM memory. Then when you restart the engine and drive the car it will learn new settings that correspond with the new tune up ect. I usually do this every spring after I have run the car and got fresh gas in it. I can usually tell a difference right off.

Tom

 

[GerryLP]

.... complete ignition tune up to included coil...

Irish,

I recall doing a search for the idle miss in my L81, and it turned-out to be that spark would jump the rotor but sometimes it grounds-out at the rotor screws.

I installed DUI's nylon screws and the idle miss went away. Nylon screws are available at Home Depot, but were more expensive. Besides, I wanted the peace of mind that they would work in the distributor. So I ordered the ones from Davis'.

Just a thought.