94 PA high idle after 'overheat'

[jrichardson]

So the story leading up to the problem: 94 PA with 200k miles

Raditor hose broke, car got real hot (half way on the temp guage) before stopping on the side of the road, cooling off, and replacing hose. Drove it home without incident...although as I remember, I think the idle was high at that point.

Next day, starts fine, but almost immediately goes to 2500rpm on idle (in nuetral). No DTC codes at all...no SES light. Car runs fine, just won't idle where it is supposed to.

After 'guessing' and replacing the engine coolant temperature sensor (the one that goes to the ECM, not the guage), and making sure all mechanical linkages are fine, I gave up and let the local shop have it.

They scoped it and said that the IAC could be bad (remember, no codes) and that I had a very, very small leak on one intake manifold gasket.

I replaced the IAC...no change. Still idles high. It's got to be a vacuum leak, I guess, because no DTC codes, right?

1. Can an overheated engine blow an intake gasket?
2. Would a small air leak in the intake gasket cause this high of an idle? I sprayed carb cleaner on the air leak and it doesn't make a bit of difference, so I know that the leak is really, really small.

My next guess is the TPS, but without a DTC code, I feel like I am just throwing sensors at it without any good reason. Is there a way to test a TPS?

Any ideas, as I am at wits end!!!

Thanks,

Joel

[DrJay]

A vacuum leak can cause a high idle but not generally that high. An expanding and contracting engine can certainly 'spring a leak' though. The TPS is actually pretty easy to test. Probe the wires going to it, you should have a 5v feed on one wire and between 0.3-0.7v at idle on another. A higher than spec TPS signal will cause similar symptoms.

Good luck!

[jrichardson]

Thanks for the info. I tested the TPS...looked good, so that must not be the problem.

Joel