Well I'm back in an XJ as of yesterday. I bought an '89 Pioneer with a 4.0, Auto trans and 4X4 with only 141,437 miles! That's pretty low on an XJ if you ask me! This thing doesn't knock, tick, or leak a drop of anything! It runs out great! I got a ride to the guys house, paid him the $300 and I got the title hopped in the Jeep and drove it home which was an hour away without a single problem! I paid $500 for my last XJ that I wrecked last month so this is the replacement Cherokee. The guy that I bought it from is the second owner of the Jeep...His grandparents bought it brand new in '89. It had been sitting for a few months so it definitely needs to be cleaned up good. It only has one problem with it...The guy told me that it needed injectors but I'm not sure if that's what it is or not. I backed it up out of my driveway yesterday and stopped, then went from reverse to drive and when it went into drive it started stumbling and then cut off. It cranked right back up but idled pretty high for a few seconds then went back to idling normal. It also kinda stumbles when I come to a stop while I'm hitting my brakes but when I let off the brakes it stops stumbling and revs back up and idles normal Oh well I can't complain at all. It's a running/driving very good looking XJ and I only paid $300 I'm going to detail it today and will have pictures up later, thanks!

 

Great find! You might have a vacuum leak in your brake-booster, causing the running issues when pushing the brake pedal. Maybe the 4.0 experts can help you diagnose better. I'm just guessing, as I've never owned a 4.0.

 

Excellent guess. That would be the first place I would look. If that doesn't help then it being a Renix I would consider the TPS and adjust it properly.

All of the above I would consider after a new set of Champion plugs. Injectors if they need to be replaced then use Ford Mustang injectors. Cheaper and more plentiful than the AMC versions.

 

X 2, both great ideas to fix this problem. I would do the following:

1.) Inspect vaccum line going to the power brake booster and the booster tiself for vacuum leaks.
2.) Clean the throttle body thoroughly to incude removing IAC and cleaning the bore and adjusting the TPS.

 

I haven't really had a chance to mess with it today but it did something else that was odd...I went out to crank it and it started and it was idling really high! It was idling so high that when I put it in gear and still had my foot on the brake it started spinning the rear tires. I quickly put it in park and shut it off. I started it again and it only did that for a few seconds then idled down and started idling normally. Could the IAC be the problem? Should I just clean it with some brake cleaner? Anybody know what size torx bit it takes? Thanks for the help!

 

Can't remember the size but it came out easily with a torx screwdriver. The TPS & related parts are looking more suspect and now that you have had the extreme high idle there is another thing to check. Grounds, they are extremely important to a Renix and I suspect yours are dirty and oily. Clean them all and any time you suspect that a ground may be at fault then make a new one. On a Renix you can never have too many grounds.

 

That first long drive is always the toughest... watching the gauges, listening for noises, feeling the wierdness of a new ride.

Enjoy the new toy!

 

I'm having some trouble. I'm trying to remove the IAC so I can clean it. The top bolt came out no problem with a T15 torx bit on a screwdriver but the bottom bolt just won't budge. The head is not stripped out or anything. I used the same T15 torx bit to try to get the bottom bolt out but it acts like it has some play in it almost like its too small to fit but a size up from the T15 which is a T20 is too big. It's getting pretty frustrating. I want to clean it out because I think my problem may lie there. Anyone have any suggestions?! Please help, thanks!!