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Help! TJ surging out of contrl on start...4000rpm+

710 Views 4 Replies 2 Participants Last post by  **DONOTDELETE**
I need help TONIGHT, cause I need to tackle this tomorrow morning (Jeep is stranded at a buddy's garage).

Here's my story. TJ was running fine, but I failed inspection due to a crack in my exhaust manifold. I spent the whole day replacing the exhaust manifold with a new one (Borla). The install went fairly flawlessly... but when I started the Jeep it just surged out of control. I had to cut the ignition. Happens with the throttle linkage off... its definitely not a gas-pedal thing. The throttle plate never moves (unless I reattach the linkage and press the pedal, of course).

What's scary is that I can't starve the engine. The put my hand over the intake I feel suction but the engine just keeps going higher and higher regardless. I have to cut the ignition after maybe a full second, for fear of ruining my engine.

All connections appear right, and no obvious leaks.

If my intake wasn't attached flush (looks right, and "felt right" during reinstall).. and had a big leak... Would this be the behavior I'd see? How does it get the extra gas?

I'm really freaked and don't want to tow or anything (just spent $400 on the part alone!). Any help is greatly appreciated.


(Jeep is a 98 TJ, Sahara 4.0)
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Re: Help! TJ surging out of contrl on start...4000

You have an intake manifold leak.

The leak profides the air. If it was small enough would just have a high idle.

The injectors provide the fuel.
Re: Help! TJ surging out of contrl on start...4000

Another alternative, since you disturbed the intake manifold, .....did you make sure that you hooked up all the related vacuum lines. To do this type of action (surging) I would imagine that it would be a substantial size line the brake booster.

Like LEVE said ..check the idle air solenoid ...but since you didn't disturb it ..and DID disturb the entire intake, I'd tend to look to the intake itself ..or the hardware that you unhooked in the process for the cause.

It wouldn't be the first time that something coincidentally occured.
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