some "interesting" idle

Okay, here's the deal. I looked this up, but my problem seems to be either unique, or it is so obvious to everybody but me, that nobody else had to ask. I love this site, and have gotten lots of good info here, but haven't posted in a while.

I have a '91 4.0L HO 5-spd. I love it. Especially the non-disconnect front axle It's at approx. 219,xxx miles. (Bear in mind the issues started after I replaced the valve cover gasket.)

On cold start, it takes a while to start. Rather than firing up it sort of stumbles it's way to life. It idles at 750 rpms, as if it's already warm. Once it warms up, it revs up to 1,500 rpms every time I push the clutch in. After a few seconds though, it idles back down.

Whatever is going on, it set off the check engine light. And it happened instantly after i finished the valve cover gasket.

My thoughts:
-I may have damaged a sensor, or vacuum line during the job.
- could the water temp sensor be messed up, and the ecm thinks the motor is hot, even when it's cold, and the car isn't getting enough gas as a result?

I could really use some ideas here, I can't afford to throw part at it with my fingers crossed.

Thanks in advance,
~A faithful Oregon Jeeper.

if the check engine light is on you can cycle the ignition switch on and off three times then leave it on and the light will flash to indicate codes. gojeeps site has the translation of the codes and a more thourough description of the process.

Go to Autzone and they will read your codes for free. It sounds like your idle air control is bad.

1993 Red XJ said:

Go to Autzone and they will read your codes for free. It sounds like your idle air control is bad.

Click to expand...

Autozone can not read his codes, he has a 91, OBD-I, autozone only reads OBD-II, 96 and newer.

You need to check all the sensor connectors and CCV vacuum lines near the valve cover and check them to see what you might have knocked loose. Sounds like you lossened a connector or vacuum line. Pull the code yourself, with the cycle deal listed in the prior post and post the code number here.