I've asked everyone I know and I'm at a loss as to what the problem is. My Cherokee starts now and idles but will not run without backfiring. I have a 96 Cherokee straight 6, 4.0. We have replaced almost everything. New distributor, cap, rotor button, fuel injectors, map sensor, idle control sensor, crank position sensor, battery, ign coil, plugs and wires, air temp sensor, new computer. We checked my fuses, pulled the o2 sensor out and it made difference, and my fuel pressure is 50 on idle and 45 with key on. A lot of people say it's a timing issue, be we tried timing it by putting the 1st cylinder top dead center and lining the distributed up right. Unless there is another method we should be using. Me and dad are at a loss and I really just wanna drive my jeep any help would be greatly appreciated.

 

Whats compression???? Did this just start all of the sudden??? Are the O2 sensorS Good??? Is it throughing any codes, was the old computer? Any air or vacuum leaks?

 

Well it started after I used a bottle of fuel system cleaner. Idk if that was the catalyst but it all went down hill after that it sputtered and backfired and I thought it may have allowed some dirt to reach my injectors and seeing as they had 300,000 miles they were already getting bad. I believed this more when I changed the fuel filter and blew through it and nice pieces of black junk came out. So I replaced the injectors. I don't know if it had any codes or not and as far as I know the o2 sensors are fine I believe he may he replaced those for me too.

 

Dad went to the dealership today and talked to a guy there and said when we can't have the distributor set on 1, that it had to move 1 gear tooth forward. Went home and fixed it. Yay

 

Congratulations, a problem you can't figure out can be the most frustrating.