k-ro958

i have a 87 comanche 4.0 stock everthing when i start it up rpm rev up to about 2000rpm then come down to about 1000 were it stays until it warms up then she would start creeping up to about 1500rpm sometime i can hit the gas and it would come down to bout 900 then start back up to 1000rpm i do have a hissing sound coming from my brake boster when i put my foot on the brake rpm comes down some could that be part of my problem i also used my meter and adjusted the tps 17% but she still revs high any ideas

tjwalker

[QUOTE=k-ro958;3446237i do have a hissing sound coming from my brake boster when i put my foot on the brake rpm comes down some could that be part of my problem[/QUOTE]

Yes. Any vacuum leak can increase your idle speed.

Replace the booster. it's going to have to be replaced anyways and could very well be related.

Bugout4x4

^^^^^ X2. And to tell for sure you can isolate the system from the booster by unhooking the booster hose from the intake port and temporarily seal up the manifold port. then start it and see if it runs correctly without the booster hooked up. But I wouldn't drive it this way.

cruiser54

And, first chance you get, go to www.cruiser54.com and complete Tips 1 through 5.