Trying to fine tune my 1987 5.7, TPI GTA idle settings. I have followed Tom Keliher's IAC and TPS procedures. With the engine at temp (closed loop) and the IAC motor fully retracted, I cannot
get the engine to idle at 400 RPM's. The lowest I can get it to run it 500 to 550 RPM's at 8 degrees base timing. My TPS voltage is right on target.

Using Datamaster scan software I notice the RPM target value is 600 the the engine us actually running around 900. Also the IAC target count value jumps from either 0 or 128 and my IAC present value is always 0. I did notice that when I turn on the AC the target idle changes from 600 to 650 as in the prom and the actual RPM also increases as expected. But what I don't understand is can't I get the car to idle close to the target RPM.

If adjusting everything at temp, what would happen when the engine is cold. Would it idle with the TB resting on the minimum air adjustment screw?

Any suggestions I would appreciate.

Thanks,

 

I finally got my car idling fine for the first time since I owned it. Turned out to be a combination of things. My timing was off a little, had a vacuum leak from a runner gasket, and It was running lean. The result of a bad fuel pump relay. If your IAC and TPS are right you can start here and hopefully find the fix.

 

One thing I do know is that my car is running lean. My BLM's are around 138 to 140. I'll richen up the mixture after I have my emission test done tomorrow.

Thanks,