tony Posted January 12, 2012 Share Posted January 12, 2012 Whan starting my '90 MJ 4.0, it immediately over-revs for 2-3 seconds and then drops back to a normal idle speed. Any thoughts? Link to comment Share on other sites More sharing options...
Geonovast Posted January 12, 2012 Share Posted January 12, 2012 Define "over-revs". Link to comment Share on other sites More sharing options...
Squeegy410 Posted January 12, 2012 Share Posted January 12, 2012 You mean as soon as it starts it jumps up to around 2k rpm's, then after a couple seconds idles down to normal? simple answer is: its a renix, so its going to do that. Link to comment Share on other sites More sharing options...
87Warrior Posted January 12, 2012 Share Posted January 12, 2012 Your idle air control (IAC) could be sticking a little. Pull off the throttle body and give it a good scrub. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 12, 2012 Share Posted January 12, 2012 Your idle air control (IAC) could be sticking a little. Pull off the throttle body and give it a good scrub. Good idea. Replace the mounting gasket when you do it or you could get a vacuum leak. Link to comment Share on other sites More sharing options...
1987Comanche Posted January 13, 2012 Share Posted January 13, 2012 Bad TPS. It's happened to my '90 4.0 twice so far. Link to comment Share on other sites More sharing options...
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