I have a new TPI V8 install in an 87 GT and after the car warms up, it idles up and down between 800 and 1000 rpm constanly. It seems to do this only after it warms up so I'm thinking after it goes into closed loop something isn't adjusted correctly. When the engine is cold the idle is steady at about 800 rpm.

It was suggested that I reset the IAC control and I got a set of instructions for that. They said to warm up the car, jump the diagnostic terminal, unplug the IAC, start the car, and adjust the throttle body set screw until the engine idled at 450 rpm??

First of all, I unscrewed that little screw so much that the butterflies were all the way closed and the engine idle would only ever go down to 550-600, and would constantly stall. So i put the screw back where it was and the idle was at about 800.

After buttoning everything back up, I'm back where I started.

Another problem that might be related has to do with starting the engine. If the engine is cold, like when it has sat overnight, it starts right up after I turn the key and roars to life. After the car has warmed up, you have to turn it over for several seconds and then the engine sputters for a second and then runs normal.

I've only had the car on the road for about 3 weeks, and haven't even put 1000 miles on it yet.

If anyone has any suggestions I would really appreciate it. I'm learning as I go so anything you might have would be great.

Your idle problem sounds like a vacuum leak.
Your starting problem sounds like leaking fuel injectors.
I would start by looking at those two things and see what happens after they are fixed.
Good luck,
tstroud

Hey Jacob, try disconnecting the battery for a few minutes, then drive it several miles and see if anything changes. It also sounds like injectors may be leaking when hot. You have the same intake setup as my vette and it starts the same way. I havent messed with it. I even had it not start at all hot a couple of times. Just waited a few mins and it started rite up. It will go fine for months, then act up a few days, then be fine again. So far the only thing Ive done about it is replaced the starter

Check the adjustment of your throttle position sensor. It should be adjusted to approx 0.54 volts.

quote Originally posted by tstroud: Your idle problem sounds like a vacuum leak. Your starting problem sounds like leaking fuel injectors. I would start by looking at those two things and see what happens after they are fixed. Good luck, tstroud

This is exactly what I was going to say but I was also going to recommend that you clean the pintle on the IAC.

Archie

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What kind of tpi engine is it? Is it modded or is it just a stock crate engine?
A lot of times the modded speed density controlled engines need more fuel pressure or they will act funny like this. Happens all the time with the V6's. A little more fuel pressure and the hunting idle will stop with them. Same can be said sometimes with the tpi V8's.

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Activities Director N.I.F.E.

Pulled codes? (from the ecm.)

No trouble codes. I'll try the above suggestions..