my 1999 cherokees exhaust manifold was cracked and i took it to a friends shop. it drove there just fine but after the manifold was replaced the mechanic who replaced it said that the engine was racing after starting and said he performed a smoke test. i went there myself and removed the intake hose and covered the intake with my hand to see if it still started. it did and the engine was racing, i dont know whats wrong with it and any advice or help is greatly needed, if anyone has had this problem or knows how to fix it itd be greatly appreciated if anyone could message me.

 

Sounds like he messed up the reinstallation of the intake manifold.

Hopefully he didnt crack it

 

If you blocked the intake hose to the throttle-body, that eliminates the IAC and throttle linkage being messed up. More than likely either the intake manifold isn't seated properly, the gasket is messed up, or he left off a bunch of vacuum lines. A smoke test is a logical test to find the leak but it's not great at finding smaller leaks, but so would looking over everything he removed to make sure it went back on properly.

 

I did the intake manifold on my 97 TJ and I didn't seat it properly and the engine raced. After a 15 minute redo of the manifold I found my mistake and seated the manifold properly. Problem solved. Start with the simple solution first.

 

You can spray a little engine starting fluid around the intake, a little at a time and find where it is leaking.

Keep a fire extinguisher handy and do this outside the garage.

 

"A smoke test is a logical test to find the leak but it's not great at finding smaller leaks,"

That is where the starter fluid shines.

 

Most likely suspect is the rear of the intake manifold (the end closest to the firewall) is hung up on the locating dowel and has left a thin gap. It can be very difficult to see from the front. It is the first thing to check when a vacuum leak presents itself right after the manifolds have been removed/reinstalled.

 

This is an easy fix.

You need to replace the so-called "mechanic".


If he doesn't recognize the connection between the racing engine and the manifold replacement, he's an idiot. He should have recognized his mistake the instant he fired it up, and he should have had it corrected before you even knew about it.

 

I agree 100%