some problems with my xj

[urabus]

I have a 92 Jeep Cherokee sport that i picked up at auction as a winter/off road vehicle. It has the 4.0 HO motor and automatic transmission. Its only visible modification is a KandN cone style filter.

Well it has two problems which i cant seem to figure out; first it idles good at start up then slowly the rpms go down and down and down until the engine stalls, It does this in traffic as well. Ive checked the vaccume hoses and all of them are attatched. Is it possibly a vaccume system leak? Second is sometimes it will start when the transmission is in park othertimes it wont. This happens frequntly and randomly. To start i have to put it in neutral. Also when it starts in park the reverse lights work, when it doesnt they don't.

Does anyone have anyinsight on whats wrong? Thanks in advance

 

[graewulf]

How do I check Pinion Bearing Pre-Load?

Check the connections on the transmission.. there is a park and neutral starter lockout switch (not sure if its one or 2) - if its loose it can cause starting problems like you describe. As for the idle problem - does it run OK otherwise? Something to try when it wont start in park.. push forward on the shifter and see if it helps.

 

[ROGLSTUBB]

I not sure about your idle problem but your starting in park problem sound like the transmission linkage needs to be adjusted. It is hard to get just right so be patient. Like graewulf suggested try pushing or a slight love tap forward might help to you get a chance to fix it. I also make sure you use your E-brake just to keep it from rolling if it slips out of park.

 

[jay79cj7]

Brake Squeal

With it running at a lower idle, spray some carb cleaner or other flamable stuff around where there could be vacuum leaks. Intake manifold, etc. If the engine revs, then you found a leak.

 

[Bounty__Hunter]

Neutral Safety switch (mounted on the transmission) is what's causing the starting problem.

The engine problem doesn't sound like vacuum, I don't think a vacuum leak would kill the engine. Sounds more like the IAC (Idle Air Control) motor mounted to the throttle body. Is the check engine light coming on?

 

[Bounty__Hunter]

www.dirtdevils.org/briantechtippage.htm

 

[90Xjay]

A vacuum leak usually caused high and uneven idle. Nonetheless, check the two small plastic lines coming out of the firewall just to the right of where the coolant tank it. One of them goes to the heater control valve on a heater hose and the other goes up around the battery tray and I think to the vacuum pod inside the front bumper on that same side.
Those two lines will rot and cause you alot of problems especially with your heater and a/c controls. To repair them just cut out the bad part and slide a slightly larger rubber vacuum line over the ends and make a patch.
I have to agree with the others on the starting, a neutal start swich can cause all of the problems you listed. Easy to replace.

 

[urabus]

thanks for the replies, i'll try cleaning the neutral switch tonight. As for the idle problem; no the check engine light is not on. The rpms gradually fall untll the engine stalls. At stoplights i have to slide it into neutral and rev up. It idles good for a while and then this starts to happen. When i re start the idle is also good for a while.

 

[Bounty__Hunter]

Abercrombie & Fitch

I'd remove the IAC motor and clean the throttle body and IAC housing real good. It's easy to remove the entire throttle body for a good bench cleaning.

 

[urabus]

well cleaning the IAC motor and TB solved the idle problem.... Is an idle around 400rpm normal?

I still havent got around to cleaning the neutral switch tho

 

[Bounty__Hunter]

I thought normal was over 500, but sounds fine if it idles smooth.