Quote:
Originally Posted by LarryGLack
1992 s10 4.3L CPI 4WD
I always thought it idled a little fast, but not fast enough to cause a problem... but over a couple days last week it got to where it runs at 35 mph with no gas pedal input. I drove the wife's because its hard to stop with the engine running that fast. (auto tranny) I checked the Idle Air Control valve and it was gummed up, I cleaned it and put it back on with no change in symptoms. There are no codes, at least the check engine light is not on. The light turns on with the key and shuts off as soon as the engine starts. I put a new IAC valve on, no joy - same problem. I removed the new one and set it on the engine, turned the key on without starting and observed no movement of the valve in or out. I pulled the plug off the valve and tested the first outside connection I came to, the test light was steady bright, the next connection in line was dark, the 3rd one bright, the 4th dark. It runs fine except for the fast idle. 220K miles. I understand when the key is turned on the valve should adjust itself in and out under ECM control. My question is - is there any ECM input that will stop this initial calibration or is the only option a bad ECM? I did plug and unplug the connectors at the ECM - no change. Everything else on the rig works like its supposed to....
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With a high idle and no vacumn leaks and gas pedal not sticking IAC is working.
Remove TBI body and clean carbon from bottom ports and buttery fly and replace TBI base gasket.
9 times out of 10 the base gasket will be sucking air.
Let us know how it goes.