'91 S-10 High Idle

I recently purchased a 1991 S-10 w/132K miles on it. When I start it, the idle is understandably high, but even after warming up, the idle is still high. Has anybody experienced these problems?
Thank you.

Ran into this a couple times, usually a vacuum leak. The fuel inj. will compensate up to a point but a leak will make it idle faster. And a bad temp sensor reading to the ECM will also cause this. A scan of the ECM will usually pinpoint this deal. Look for real low counts on the IAC (idle air control) and the coolant temp readout.

You didn't list an engine size? If this vehicle has a speed density system, then a vacuum leak, could cause the idle to go high.

Did you check for trouble codes?

Did you check to see if the throttle valve is closing? What does the tps sensor show?

Thank you, I will check for a vacuum leak.

also remove and clean the IAC valve in the side of the TBI unit, commonly is all carboned up and it controls idle speed

just unscrew it from the unit and use carb cleaner real godo on it and also in the hole in the tbi unit it comes out of and then compress air blow it all out good


lots of black crud in there, get it out

if its really bad then you should remove the unit and do it from underneath too

good luck

Thank you for your response.
I am a neophyte at this.
What and where is the IAC valve? What and where is the TBI unit? Will I need any special tools?
Thank you again.

hi there the IAC is the big thing sticking out of the side of the tbi on the passenger side of the unit and has a big 1" or so hex on it for a big wrench to fit it

a coupel wires plug into it, usually four and is a square plug shaped like a transmission converter lockup plug is

cant miss it

look at this too:
http://autorepair.about.com/cs/troubleshooting/l/aa042603a_08.htm


your distance of pintle extension should be 1 and 1/8"


good luck

Thank you very much, I am now ready to tackle this job.

Thank you very much, I am now ready to tackle this job.

Has there been any progress on this issue? I have just about the same issue with my 95 S10. We replaced all of the bad hoses we saw, I cleaned the throttle valve and I also replaced the throttle sensor (which was sort of strange because I had to turn it 1/4 cm clockwise to get it flush, then turn it back to be able to put the screws in)

2 weeks prior I had to replace the power booster because my brakes no longer were "easy" to use :)~ I dont know if this relates to the problem, but everything I have googled so far the high rpm's and brakes seem to go hand in hand for some odd reason.

I did clean it, and it seems to be a bit better. It was dirty.