Vacuum?

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

That is a big vacuum leak. Did you leave the brake booster line loose? Is the butterfly in the throttle body seated?

I can't wrap my head around this. The butterfly would have to be open, probably wide open to hit 5k rpm.

Left my booster vacuum off one time and it only went to 2500~. I'd suspect that new gasket or something holding the throttle open like mentioned above.

Also, just as a precaution double check all the sensors are connected and didn't get damaged.

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I'm wondering if the TPS (throttle position sensor) is jacked up.

If you unplug the tps the rpms would change if it was the source right? If so, worth a shot for free!

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