I recently replaced the freeze plugs on my 99 Cherokee Sport 4.0.

Once I had everything back in place I started it up and it immediately ran up to the redline and I shut it down. Checked everything and tried again. Same result.

I loosened up the intake to make sure I had it on the guide posts. Everything appears to be in the proper place and torqued in the proper sequence.

Today I had a friend with me and when I started it we could hear a vacuum leak at the rear of the engine. I have a new manifold gasket and we both inspected it and everything seems to be sealed properly.

Could a vacuum leak in one of the lines cause the engine to rev to the max?

Would resetting the PCM do anything?

RSWiser