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Discussion Starter · #1 ·
I have an 88 S10 with a 4.3 and it seems when driving the truck each time I let off the gas pedal this slow to get back down to a normal idle speed.
I like carbureted vehicles when you let off the gas pedal it instantly drops down to an idle. With his truck if you rev the engine it goes up and then slowly comes back down but rarely gets to a normal idle.
I went online and found a handful of videos showing how to clean the idle air control valve and then reset the idle.
That sort of worked but then went back to a higher than normal idol which is always had.
I said heck with the cleaning and bought a brand new idle air control valve. It idled high also, so I went through the routine again.
This video shows the routine I've seen in a handful of other videos. The only thing missing from this video is that it was mentioned in other videos, after setting the idle speed screw, to remove the battery cable for 5 minutes and then plug the idle air control plug back in place before starting the vehicle.
Numerous places show this same sequence.
So the new valve was installed and the idle was quite high. It's been mentioned to drive the vehicle around a little bit and the new pintel should adjust itself to normal. I drove it around about a mile and when I came to a stop the idle was around 650 to 700 and I thought all was good. I drove it around town, up over hill down the other side to a stop sign and it came back down to a good idle again. Every time I came to a stop sign the idol went back to normal. Cool I thought this sucker is fixed!
Pulled into a mini mart to get a six pack of beer and go home and when I turn the truck on the idle was back up around 1500 and wouldn't come back down. It's been that way for the last few days and sometimes the idle is even higher than that.
This video mentions checking and adjusting with the throttle position sensor. I haven't done anything with that.

Is that my problem?
If so, do you guys have a procedure for checking and adjusting the throttle position sensor?
 

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Discussion Starter · #2 ·
50 views I think I'm on my own. I'll give this a shot. My engine is throwing no codes.
 

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There is no adjustment for the TPS. It can bind and cause a high idle. Try a new one.
Messing with factory set base idle screw just helps folks who don't understand the idle system on a TBI. As a dealer tech we were not allowed to touch it. That's why they have the anti tampering cap. You might have a vacuum leak. Put a gauge on it. The base gaskets are known to leak. Or the TB maybe in need of a rebuild. Remote possibility is a faulty ECM. Rare, but can happen.
Do a search on here for high idle. I know I posted the IAC install procedure less than 2 weeks ago.
 
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