Hey all, I haven't been on for a while cause I sold my last jeep. But I just bought another one to play with. Its an 88 Cherokee 4x4 with the 4.0 and automatic. I bought it not running as a bit of a basket case but after putting in a fuel pump, starter, muffler, plugs and wire, and a new cap and rotor I got her running. It runs ok and for only having about $400 in it I can't complain. But I'd like to get it running better if I can. I know the early fuel Injection sysetems weren't so good but maybe what I have is a common easily fixed problem. The motor runs good when under a load and high rpm but at idle it lopes really bad and when revved in neutral it smokes and misses. The smoke is black and it's acting like its running rich, is this common with these early motors? Also is it possible to replace the throttle body with a carburetor and just get rid of the fuel injection totally? This is just a toy for me to play in the mud with so I'm not worried about smog or anything. And I figure a carburetor would hold up better for mud and water anyway.

 

Bump, after searching I found people with similar symptoms were having trouble with their MAP sensors. Could this cause my loping and rich idle?

 

ya i have a renix too...if you do some searching you'll find plenty of info on here about MAP sensors, TPS sensors and the like. sorry i'm no expert, but everything i've needed to know for my rig to this point i've just searched this site and come up with good results every time. i dont need a haynes manual...yet.

change that MAP vacuum tube and go from there...

 

Yeah I'm going to start with that. And double check the wiring to it. I'm not real familiar with jeep fuel injection systems. All the ones I've ever had have been carbureted and idiot proof

 

Vacuum hoses as hank suggests. The MAP sensor is on the firewall with an electrical plug and a vac line that runs down to the passenger side of the throttle body. Carefully inspect that hose. Make sure it is clear, no cracks or melted spots. Also be sure the orifice in the MAP isn't clogged up and it's electrical connector is tight.

 

Well it was the MAP. The previous owner had for some reason bypassed it. The vaccume line had been unhooked and plugged. Hooked it up and the Jeep runs 100% better, it idles nice and smooth. And it doesn't smoke anymore either.

 

Every one needs a manual !! LOL