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Discussion Starter · #1 ·
Two weeks ago i took a 150 mile trip to the coast and the header on my Tj completely ripped apart just below the collector tube. It happened the first night of the trip so i i had to park it all weekend and trailer it back home. Two weeks later the new one comes in and i stay up all night putting my jeep back together. No problem! this isn't the first time i have taken out that header. Finally ready to start it and the it turns over fine and then all of a sudden the RPMs just take off! As soon as i start the jeep it begins to rev and it seems that it would readline if i didnt cut the key off! It ran fine when the header broke it just sounded like a monster truck!! My check engine did come on i think it was because of the O2 not reading. But the check engine is gone after disconnecting the battery. The throttle is not getting stuck and the linkage is not tight of sticking. Any help would be much appreciated! I need my Daily driver back!
 

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this question was asked on another board and these are the answers they got.


"Check the O2 sensor. I had a similar problem and the O2 sensor was the culprit. When the O2 sensor dies, the computer thinks it is running very rich and so tries to blow out the excess by revving (at least that is the way my mechanic friend described it)."

"My 98 TJ did the same thing if you still have the stock gasket, align the 2 , My borla header came with a gasket that was a 1/4" difference in the intake holes, I had mine apart 3 or 4 times before I realized it, it was so fun.. as you know."
 

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Discussion Starter · #3 ·
That is very helpful. Thank you. Is there a way of testing the O2 with out a diagnostic machine?
 

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Discussion Starter · #5 ·
Yeah i definitey tried the battery which cleared my check engine light but did nothing for the high rev.
 

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Jack Lives Here!!!
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I'd be more inclined to go with there not being a proper seal with the gasket on the intake.
 

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Discussion Starter · #7 ·
i would like to think that it was a seal problem but it's just so odd how the engine will instantly redline. It seems like only i second that i leave it on and have to turn it off when the rpms reach 4000!
 

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Jack Lives Here!!!
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That's exactly what it will do if the intake isn't sealed properly. It's kind of like a vacuum leak. So it's running wide open.
 

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Discussion Starter · #9 ·
Yeah when i think about it i dont know what else it could be everything was fine before. I guess i get to take it off again!
 

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Yep I agree with the others that there's a 99.9% chance its a vacuum leak at the intake manifold. That's a common occurance after replacing the exhaust header. :)
 

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Discussion Starter · #11 ·
99.9%! I like the sound of that! that will be a easy fix then even if it takes some time. Beats buying new sensors.
 

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Discussion Starter · #12 ·
IT WAS AN INTAKE MANIFOLD LEAK!!!!!!!!!!!!!:eek:

next time i lill wait for some daylight!
 
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