So my 88 Renix which has a mind of its own has been giving me some funny issues. I am in no way an expert mechanic so i'm having some trouble identifying the issues. Recently, my 88 cherokee began gulping gas (around 7mpg.) Its running about 500 rpm idle, smells rich, engine shuts off when reved above about 3500 rpm, and just recently started producing black smoke from the exhaust. The weird thing is, most of these issues seem to go away once she hits the trail. Any ideas on where I should start?

 

sounds like a pcm to me.

 

He's got 7 posts, maybe he's new to XJ's... does he know what a PCM is? Just sayin

(yeah he can Search i get it)

 

sounds like the main computer to the jeep. fuel map is out of wack. or o2 sensors any check engine light on?

 

I know what a PCM is, im already working on getting a new one to exhaust that option.

 

Renix jeeps don't have a check engine light. **** just happens

 

As i looked further into it it looks like the PO may have done some butchering of my wiring so i've got a buddy coming to check out my wiring this weekend, hopefully i can get my hands on a PCM by then. I assume any PCM from any renix will work?

 

First off, the Renix Jeep has no PCM. It has an ECU. This could be as simple as a messed up vacuum line to the MAP sensor.

 

Sure enough, I just checked the vacuum line and it was busted, must have broken it without realizing when I was messing with my TB. off to buy a new one, hopefully this solves the problem.

 

I just used some vacuum line, broke the map tube so it was a short section that was straight, and yapped it with the smaller line from my vac ball, I relocated the ball but didn't trim any of the line off. Its actually come in handy a few times.

 

I went ahead and used my favorite fixer, some tyvex tape, its like duct tape on steroids.

 

uh you need a vacuum connection from your throttle body to the sensor, otherwise it won't run right. Id recommend using a hose of some type

 

Yea, i used the hose that had broken. Just taped it back together. I plan on getting a new hose next time i go to the parts store.

 

Woohoo. A simple fix.

 

Hopefully, thanks for the reply really helps a young guy like myself improve my XJ knowledge!