Originally Posted by Superclyde

I have a 99 cherokee 4.0. Its throwing a multiple misfire code. What it is doing is hard to explain. I believe it is misfiring infrequently, but getting worse. This misfire, or bucking, as I call it can happen at any time while driving or idling. However, it is almost guaranteed to happen when shifting into reverse or turning right, to the point that the jeep will die. The bucking will also be aggravated by our bumpy county roads, but wont die. Only dies when turning right or shifting into reverse. Its crazy, this bucking has happened in all driving conditions, but seems to happen more on bumpy roads. It has also done it on start-ups but give it a little throttle and it will revert back to a smooth idle. Sometimes you can drive it 70miles and it will buck only a couple of times, other times you can go 5 miles and it wont stop bucking. Getting pissed because my mechanic and I can't figure it out, and I'm not ready to call it quits on my jeep. It does have 186K on it but has been well taken care of and been extremely reliable, no major issues.

So far I have replaced plugs, wires, cap, rotor.....the usual stuff, no luck. Mechanic thought it was a fuel issue, so checked the fuel pressure but it was good at 40psi. I changed all 6 injectors as he recommended, still have same problem, same multiple misfire code. I questioned the CPS and TPS, but mechanic said doubtful as the code does not indicate either. Last night checked for a wire shorting out, didn't see anything in the dark. Another mechanic said possibly the ignition control module? I'm stumped, ready to take its misfiring *** out to the pasture and put her down! Help, I'm dusting off the 12 guage now

Originally Posted by Superclyde

I was really close to putting in a new distributor when I found the problem. Thanks to the advice on this thread I was able to find it. It was the ground strap from the rear of the engine to the firewall. It wasn't loose at the engine or firewall, which is why I probably didn't catch it the first time. However, because of the way it was routed, it was shorting out on the brake line. I had the engine running when I was checking grounds. When I moved the ground strap, the engine missed and instantly died. Upon further inspection, I could see a spot on the ground that had been rubbing the brake line. My guess is that it wasn't touching all the time but enough to cause the misfires. Removed strap, cleaned connections, installed strap (different route) and have put 100 miles on it without a single incident. On the road again trouble free and once again a happy camper, but not without a minor heat stroke in the driveway followed by a slew of cuss words thanks everyone.

Originally Posted by Rudy

Can't miss it, it's a braided metal strap bolted to the rear of your engine on the right side and bolted to the firewall just right of the map sensor.