RPM surge after lift installation

I just installed a 2.5” lift and on the first test drive I noticed a new issue. When I push the clutch in, the engine rev’s to 2000- 2500 RPM for a couple seconds then goes back down to 750 RPM. I’m not sure if it’s a result of the lift, or a coincidence that it just start happening. Also it’s notable that the temperature outside was -3°F but the engine was warmed up.

I’ve also read that it could be an issue with the TPS or maybe vac line leak. There are no Check Engine lights, yet.

2003 TJ, 200k miles, 4.0 L.

Any thoughts?



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Are you running bigger tires? If yes, re-flashing the computer might solve the issue.

Good thought, but no. Same tires— for now. Thanks.


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From my limited experience with the 4.0 so far, a vacuum leak is probably the culprit.

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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

Update: The issue seems to have gone away now that the weather has warmed up to 30°. But still, I’ll check for vacuum leaks and update this post.


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