1989 Chevy Truck jumping idle

1989 CHEVROLET TRUCK
230,000 MILES • V8 • 2WD • MANUAL
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ISAAC302
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I have 1989 chvey 1500, with the 305 tbi, and 4 sp with o/d manual tranny.
The problem: When you start it it turns over fine, revs, then it looses rpm sounds funny then alomost dies, and Revs all the way back up. It repeats this cycle for a few minutes then it will kill itsself.

I have taken off the air cleaner, watched it run, saw plenty of gas coming out of the injectors, I srayed it down with TBI cleaner. Then I tryed testing sensors; idle air control valve and throttle position sensor. I used my volt meter seemed ok. I dont know where to go from here.

Thanks for your help.
Isaac
Dec 5, 2007 at 4:48 PM
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RASMATAZ
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Hi and welcome to 2carpros

The main function of the idle air control valve is to target the idle and return its signal back to the computer at which time the computer computes by looking it up as programmed then send it back to the IACV to control the base idle.

You need to open it up and inspect it and clean the air passages involved in it, Furthermore test the throttle position sensor this one is also involved in the position of the throttle plate that the computer is relying on to control fuel enrichment. Check it out and if further assistance is needed come on back.

The exhaust gas recirculation valve could also cause this problem
Dec 5, 2007 at 5:07 PM