Hello all. On my 1989 Trooper II, I notice my idle is usually around 1300-1500rpms. Seems a little high don't you think?

Also, I noticed a couple times while sitting at a stop light that the idle goes up and down from 1500 - 2000 rpms. It's almost like I'm revving up the engine.

Any suggestions?

Is it running too warm/hot? If so, I would say your coolant level is too low. When the engine is cool, pop the radiator cap and see.

Beyond that, sounds like a classic vacuum system leak. Check all of your vacuum lines/connections for leaks/cracks/holes/etc and replace as necessary. HTH <img src="/forums/images/graemlins/cheers.gif" alt="" />

...and don't forget the TB (or carb) to manifold gasket..

I just had this problem last week. Like Sean said, my first thought was a vacuum leak. Turned out to be the throttle body linkage was sticking. Cleaned it out and lubed it and it now works like it should. Check that in addition to the vacuum hoses.

Thanks for the info!!

It doesn't seem to be running hot or cold according to the gauge.

How much should a shop charge me if I ask them to check these things out?

Also, what is a good idle speed for this troop?

P.S. Just bought this 89 Trooper a few weeks ago and really, really like the beast. Went 4 wheeling this past Sunday and had so much fun.

Just solved this exact same problem in my '89 (2.8L). <img src="/forums/images/graemlins/lol.gif" alt="" /> Things to check (in order of hassle/cost): First, check all the vacum hoses for leaks. Second, check to see if the idle air speed motor in the throttle body is dead. Third, check for leaking throttle body gasket. Fourth, check for leaking intake manifold gasket (NOTE: check the INSIDE of the manifold also - by this I mean toward the middle top of the motor). Fifth, check to see if the control assembly for the throttle body plates is loose. Part of this assembly is a shaft which goes through the wall of the throttle body toward the bottom. When I checked mine, it moved A LOT and the idle speed changed as I moved it! The bushing around the shaft was worn-out - acted just like a vacum leak. The bad news is that you can't get a rebuilt throttle body for a 2.8 ANYWHERE! You can rebuild it (kit is around $135.00) but this bushing is not part of the kit. The good news is that a throttle body for a 4.3L GM bolts right on with minor mods to the linkages. I did this to my '89 (used throttle body from a '90 GM cost $85.00 from a wrecking yard) and it runs like a striped-ass ape!

Someone else had a problem similar to this not too long ago. It turned out to be rats or mice eating the wire insulation. So. . . check for vermin too. <img src="/forums/images/graemlins/lol.gif" alt="" />
Jim