Hi all.

1996 5.9L 1500 2wd 203,500 miles, auto trans

Scenario:
After driving to work ~25miles (the truck has had a chance to full warm up), I stop, put it in park and the idle climbs to ~2k rpm, then falls to 800 rpm and continues to sit and surge from 800-1000rpm.....

But, if I restart it, the idle does its normal start_up_surge and then falls down to ~650rpm and sits and idles perfectly.


any suggestions on where to start?

How tight does the oil breather/filter need to sit in the valve cover? As tight as the pcv valve?

thanks,
Chris

 

I had the same problem on my 1999 Grand Cherokee. I replaced the Throttle position sensor on the throttle body and that seemed to fix the problem. You might also want to check your O2 sensors, those might be going bad. Hope this helps!

 

Mine did that but only when cold. A new AIC fixed it.

 

thank you.

I am leaning towards the TPS rather than the IAC b/c of the fact that cold morning, starts and idlingare ok. The problem only happens after the truck has been driven a while.

Any way to test the TPS with a voltmeter?

 

I'm having the exact same problem, except my truck only idles like that maybe once a month. I'm gonna start looking for the problem based on wht you guys said. Let me know if you find what the problem is.

 

Mine started out like that too, maybe once or twicea month and progressed to once or twice a day. Had the dealer install a co-pilot to try to track the problem but they came up with nothing. Just decided in the end to replace the sensor anyway.

 

Try cleaning the TB with carb cleaner.A bit of built up dirt or carbonon the butterfly will keep it from closing all the waycausing an idlesurge.

 

There is a procedure spelled out in the Haynes to backprobe the TBS. It's a real bear getting pins to make contact just right.

With your idle fluctuation like that, it makes me think it could be the Evap Purge Solenoid. I had the tubes to mine connected in the wrong ports when I reinstalled my engine, and the idle fluctuated like that. Swapped them and it stays rock steady.

Just another avenue for you to check.

 

http://www.v8performance.com/tipsandtricks.htm tells you what the voltage should be and how to check it