I got my TPI running yesterday. (swapped 88 MAF TPI onto my old carbed 350). Now I am trying to tune it and get it running well. I am having a problem with my idle. Once the motor runs for a little while (1-2 minutes) the idle gets real erratic. It dips, picks up, dips picks up, etc. The more it runs the worse the idle gets. It will eventually stall out.

I reset the TPS. It was at .570 volts and I set it to .508 volts.

My 0xygen sensor is not installed right now. Would this do it or contribute?

Also though if I rev the motor up (say 3K) and hold the throttle there the RPM will stay for a few seconds then drop down (2K) and pop up some and drop again, etc.

I am thinking my TPS might be bad but I don't know.

No codes are set though. (beside 12) and the check engine light doesn't appear while the motor is on.

 

Not having the O2 sensor hooked up wouldn't cause a problem like this. The ECM isn't even taking a reading from it until the car is fully warned up.

Sounds like a vaccum leak problem. I'd go over all the lines and connections. A good trick is to spray them with carb cleaner. If the idle races then you've found a leak.

If there isn't a vaccum leak then I'd suspect the IAC. You can adjust the IAC steps by turning the throttle stop screw clockwise. There may be a plug over the set screw. Just remove it and you can access the screw. Adjust in 1/2 turn increments. You'll have to reset the TPS voltage after each adjustment.