1993 GMC Sonoma Idle speed Way Too High

CATFISHER12

MEMBER
1993 GMC SONOMA
6 CYL
2WD
MANUAL
145,000 MILES

This is a 2.8L TBI 6 cylinder 'Z' engine. It has been sitting for 2 years with body damage; but is now repaired.

With fresh gas it started easily and runs fine, EXCEPT that it is idling way too fast. It can be hard to get it into reverse and I don't want to hurt the clutch. All I need to do (I hope) is slow down the idle. There is no AC to affect anything.

In trying to research this I am finding 2 opposing ideas. 1: There is no adjustment possible, it is all computer set thru some sort of vacuum control. 2: There is a curb idle screw to set by a solenoid and a base idle screw on the side.

I dnld'd a picture of the carb showing the adjustment screws from Auto****, I will try to attach it here. I would like to know what to do to slow the idle down.

Thanks so much.

1 Reply

HMAC300

MECHANIC
48,601 POSTS

With that fuel setup the TBI units would blow teh gasket below the TBI. It would cause a high idle among other things. It should be a simple fix, just go to auto parts store and get another gasket, thick on preferably, then unbolt the tbi unit and replace the gasket. You just need to lift the tbi up an dput the new gasket in place as long as the old gasket is cleaned up.