Working on a friends 89 5.0 5sp ex FHP car. Engine rebuilt, B cam, cobra intake and 65 TB. He was having idle problems and acted like it has slight miss. Ive got an old Brainmaster scanner and checked codes. Only one was O2 showing mixture rich, which makes sence with that cam. I adjusted the idle speed and set the TPS to.995. Then I ran a cylinder power balance test and it show all the cylinders even, We took the scanner off after deleteing the codes and drove it around the block and as we pulled into the driveway it started acting like it was going through the balance check again. Cleared the computer and it seemed fine and took it out for a drive and you guess it, it started to idle up for 30 seconds and then back down. Pulled the IAC wire off and still does it. The computer is doing it through timing. We checked and doubled checked the grounds all seem good. Anyone ever have this happen before. What do I check next.
Bill
Bill