rev's up to redline at startup
 

I have a 99 cherokee with the 4.0. I replaced the intake/exhaust gasket yesterday. After putting it all back together, as soon as it starts, it immediately rev's up. I have to shut it off b/c it will overrev if left running longer than 3 sec's. All the electrical connections are good, I have recently replaced the TPS/IAC. The only thing of note is that I scrubbed the block when I had the intake off and I replaced the O-rings on the injectors while I had the fuel rail off. I wiped each injector off and cleaned the accumulated varnish around the tips of the injectors with some carb cleaner and a rag. I am stumped as to what is causing this. Any ideas? :wallbash:

large vacuum leak

Is it possible the new intake gasket is leaking? I don't have a torque wrench but I tightened the bolts down like I would've on any of the other motors I have worked on. I worked center out, tightened them incrementally, and got them pretty damn tight. The only thing I can think of would be TB gasket. I did reuse the old one.

check intake from under neath with flashlight they do get binded up on the alingment dowels causing a leak

^ what he said

one more thing throttle plates closed right not stuck open just a thought .

I even saw once, where the guy tighten the heck out of it when it was hung up on the pins, cracked right through between cylinder 4 and 5

Good idea. Going outside with a flashlight right now! I'll post back on what I find.

Problem solved. The intake was sitting an 1/8" low causing it to be propped up on the dowels. Very difficult to see without a big flashlight and really looking HARD. Thanks for help!

Great news ...