My 92 Firebird V6 3.1L has started to shut off when the car slows down, with or without the brakes applied. The idle drops to 500 rpm, then about 300 and then it's dead. This is with the engine at normal temp, right off the highway, whenever.

Also, at initial startup, the idle suddenly jumps to about 1200 rpm from around 300. It used to go up smoothly.

TPS? What else can I check?

 

I'd check the IAC before the TPS. In fact, I think you have the non-adjustable TPS (unlike 85-88 2.8's), so the only "adjustment" you can make is a replacement!

Buy "fuel injection tuneup spray", or "throttle body and intake cleaner for fuel injected engines." Try to avoid carb/choke cleaner, it attacks fuel injection stuff. The stuff you should buy is usually sold near the carb/choke cleaner. I use Gumout's stuff, yellow can & red top.

The IdleAirControl motor is at the top passenger side of your throttle body. Turn the car off and hide the keys- don't turn the car on with the IAC removed from the TB! (It's not -bad- if you do this, but the IAC will over-extend itself, and you'll have to do additional work.)

Unplug the IAC, remove it with a large open-ended adjustable wrench. Keep note of the "strength" you use to unscrew the IAC. You'll have to put it in about as strong- not too strongly. The IAC motor is steel, the TB is aluminum, and you can strip the hole.

With the IAC removed, hold it so the pintle faces DOWN. If the cleaner gets inside the IAC motor it'll ruin it. Spray the cleaner onto the extreme end of the pintle to get the carbon crap off. Let the IAC dry with the pintle pointing down.

Now, remove your air-intake-to-throttle-body hose. You want to spray the intake cleaner into the hole that the IAC came from- this will clean out the IAC passageway. The passageway runs from the back of the throttle body blades, up to the IAC, and then out the front of the throttle body. It's a small hole that exits on the passenger side of the TB, inside a recessed slot. Spray the cleaner in there and watch the carbon come out the front hole. Spray until you see no more carbon.

Put it all back together. I've always re-used the IAC-to-throttle-body gasket, I suppose you can cut your own from a sheet of thin black gasket material (found at any parts store by the gasket sealants).


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Thanks Tom, but I forgot to mention that I already replaced the IAC sometime ago. I just bought the tps and will test it later with a voltmeter with Jester's help.

 

did you clean out the tps passage? it tends to get carbon buildup.just spray a bunch of carb cleaner in there, and reset minimum idle

the tps is adjustable on all cars it just needs some modification