Chevrolet S-10 idle speed

DERITA.MICHAEL

MEMBER
1991 CHEVROLET S-10
6 CYL
2WD
MANUAL
93,000 MILES

Hello, I have a 1991 cherolet S10. The truck has 94,000 miles, has a six cylinder, 2.8 liter motor. Five speed manual transmission. I have recently purchased the vehicle, I know almost nothing about the truck except the Idle speed is around 2500 rpm's. My truck in the state of washington will not go through emissions testing becuase of the idle speed. I think the previouse owner was trying to make the truck more fast, there is also five, 1 in diameter, holes bored out in the air filter covor. I would like to know how to tune down the idle speed of my '91 S10 from 2500 rpm's to 950-1100 rpms, at Idle. Could you please help.
I have had some friends look at my S10 and most of them look for an adjusting screw, because my car is carburated, or my friends say there is some sort of vacum leek. I havn't found the adjusting screw yet, and I don't know what a vacul line looks like. Thank you for your help.
Michael De Rita

1 Reply

LEGITIMATE007

MECHANIC
5,121 POSTS

That is why the idle speed is so high, because of the vacuum leak, he probably purposely removed it, a good way to check for a leak is to, mist some carb cleaner around all of the hoses until you hear a change in idle, that is the spot where your leak is. Check for the pcv and egr valve, that may be where your leak is, you can also listen for a very high pitched whistle those holes in the air filter, will cause the high idle too, cause you now have a huge vacuum leak