Idles like crap in gear and smooth in park and Neutral

[Tim88XJ]

88 Jeep Cherokee Limited all stock, 140k. The problem is intermittent, and when it comes, it is usually warmed up. The idle bounces around and is really rough. Shift to nuetral or park while sitting at a stoplight or something and hte proplem goes away and idles smooth. I paid the dealer 350+ to "fix the problem" they rewired that junction block on the driver side firewall in the engine compartment and cleaned my TB and injectors. Problem went away for a month. Now I want you guys to help me know what the problem really is. Help me out. -Tim

 

[satan]

Have you looked at cleaning your NSS?

One of the sets of contacts from the NSS is used to signal the RenixII ECU to maintain better control of the idle (basically allowing the ECU to work IAC changes more rapidly).

Assuming, of course that your tune-up stuff is all in good shape and that the dealer's work doesn't need to be revisited...

 

[XJTripp]

Like Satan alluded to I would check general tune up stuff too. If the spark plug wires are bad, they leak more voltage under load. Distr. cap and rotor are candidates too.

 

[Tim88XJ]

Has a full tuneup.... all the mentioned parts have been replaced. what are the chances its the NSS? -Tim

 

[sidriptide]

could be as simple as a small vacuum leak.... spray some carb cleaner around any connections, fittings, or intake flanges... might be a simple fix...

 

[terraman]

Take a peak at the crank position sensor and its wiring, had a similar problem last year with my 89, its just a tought.

 

[Runnin'OnEmpty]

My vote is for Mr Satan's NSS suggestion. The shifting to neutral and park with the OK idle, is the key.

 

[satan]

Me too... oh yeah... it was me...

Either that or you're looking at the extra loading of being "in gear" (where all the talk about tune-ups come from -- On a totally off chance, is your tranny happy? (full/not over-full with clean ruby-red colored ATF..)? --