RPMs Jumping.

The RPMs on my 88 Trooper II will jump by by 1k+ RPMs at a time. The ECM, spark plugs, timing unit, belts, fule pump, fule lines, fuses, and gas tank have been check for problems from electrical to garbage in the lines. While drive the effect of the RPM jump is the same as shutting the engien off for just a moment. I have taken the Trooper to the Isuzu dealership to be worked on, but they gave up.

I do not know what is wrong, and have given all info I can think of. I do not know much more about cars other then where to find the clutch. Any info will be helpful. My father is a pro, and works on cars for a living, so you don't have to worry about dumming things down for me. (and yes he hasn't be able to find the problem...he does body work)

Thank you.

My 99 did something similar to this, and it is described in the FAQ. Sounds like a bad intake manifold. Try spraying/misting some carb cleaner around the sides of the manifold while its idling. See if it makes the revs jump up...

replace Fuel Pressure Regulator

We found the problem when we took it to the shop for a full tune up. We thought it was an eletrical problem, but it turned out to be the fule filter was bad, and the gas coming out of it was black. The RPMs are good now, but just a few days after fixing that the clutch goes out and won't disengage. :banghead: One problem after another. I'll post again if we have problems we can't solve, but for now this problem is solved.