YJ revs on cold starts

[Mark]

‘95 YJ started revving high off cold start, then “sucking” occasionally while driving. Cleaned throttle but still having issues.

 

[Fouledplugs]

Have you checked all your vacuum lines?

A simply spray of brake cleaner around targeted vacuum lines should help you in your diagnosis.

 

[Jakebrake]

yup. vacuum leak...possibly more than one.

 

[Chris]

Most likely it's a vacuum leak.

 

[Mark]

Please help. My 1995 YJ started revving real high when I start it, then immediately levels off. But then when I shift gears, it appears as the throttle is stuck and it keeps revving up and accelerating by it self. I have cleaned the throttle body, and even replaced a broken throttle return spring, which I really thought was the problem. No luck. Any help
Mark

 

[Flyer58]

The throttle body has an electric idle control valve which tends to get gummed up causing a high and slow to react idle control. Inside the throttle body you'll see an oblong opening on the inside wall and be sure you get plenty of throttle body cleaner inside there. You can remove the controller and clean the little plunger too just don't lose the screws. It may need replacing it this continues after cleaning.

This is just my initial guess since I've had it happen several times.

 

[Fouledplugs]

Noticed you posted a new thread. Have you checked your vacuum lines?

 

[Chris]

I've merged both threads. There is no need to start two threads on the same subject.

 

[Torched]

Making more air available will cause revving (vacuum leak, carb tolerances or gaskets). You may notice lean symptoms, like popping or white plugs. Booster is a big sucker so if leaking intermittently with brake actuation it would affect RPMs. Anything that allows more air past/under throttle plates will rev engine. The jets don’t know if you added more air with pedal or a leak has occurred.