My 89 Vandura 5.7 lit. idle's so high that when I put it into gear it slams pretty hard into gear. Anyone know how to adjust the idle or whatever I need to do to fix the problem?


Asked by Jan 22, 2015 at 02:34 PM about the 1989 GMC Vandura G3500 Extended

Question type: Maintenance & Repair

Idles high and I can't find any kind of an adjustment screw or anything to adjust. anyone
have any ideas?

1 Answer


Vacuum leak. Unmetered air entering throttle body will cause high idle. There is no adjustment. Or I don't know if a 1989 has a TPS, Throttle Position sensor, it probably does. The butterfly in the throttle body may not be closing all the way. Listen for a sucking sound, or hoses off, or nipples with nothing attached, all will cause a vacuum leak

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