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Hey all, new to the forum, been using this and jeepforum for the past 2 months to keep my MJ up and running. Quick history on the MJ then I'll give ya the dirty dirty: Swapped for the MJ (4x4, 4.0L, Big Ton, with 5-spd) about the end of August down in NOLA. Exhaust manifold wasn't connected, but otherwise it ran great. Drove around town like a bandit then left a week later to Alanta with no issues other than gassing myself in slow traffic (also, possible hearing loss). In Atlanta, bought nuts and reconnected exhaust. Much quieter, ran good for another tank of gas (300 miles maybe less) started idling rough. Pulled plugs (they were shot, maybe even original to the jeep). Replaced with Autolite 985 copper core (gapped to .035" I'm pretty sure). Fixed idle issue. Loaded up and headed back to NOLA. Left mid afternoon, got a hesitation or two along the way, could have been a bump in the road. I get about to the La. state line (about 11pm) and the truck starts misfiring and surging erratically. Hold the throttle and try to cruise at any speed/gear/rpm and it bucks and fights. Under hard acceleration the problem is there but much less pronounced. Let off the throttle and the issue seems to go away (truck isn't shaking anymore, hard to tell over hwy noise). No CEL at any time. Limp into NOLA and over next 3 weeks: Replaced Fuel filter- no change Tested fuel rail pressure and flow rate- ~31psi and 39psi with regulator connected/disconnected. With return pinched off flowing close to 2l/min (filled 500ml bottle in 13 seconds). Pulled spark plug wires and checked for resistance...all were similar with longer wires slightly higher than shorter wires. Cleaned ends and reattached (all done one at a time then double checked for order) - no change in symptoms Pulled old O2 sensor and bench tested. Readings very erratic. Order new Standard SG1829, bench tested it to compare readings. New one cycles as expected from .1-1.0A in flame. Installed new O2 sensor and problem appears to be fixed. Test drives, no bucking, no skipping. Next day leave NOLA around 4pm, drives great for first 150 miles. Pouring rain, temps drop and from around Lake Charles to Victoria, Texas the misfires are as bad as ever. Pulled over several times and disconnected/reconnected O2 sensor trying to get the ECU to run the motor rich, used ether to locate at least one vacuum leak (repaired with electrical tape), tried plugging vacuum lines, looked for spark leaks, wiggled wires and lines, dumped in a bottle of B12 Chemtool and 89 Octane out of desperation, nothing. If driven at high rpm the misfire is dealable but anything below 2000 rpm I'm afraid I'm going to blow the bottom end of the motor out unless I'm accelerating WOT. Then, after taking a nap in Victoria I wake up this morning, fight the misfire for about an hour and after the sun comes out and it's 84 outside, the truck drives with no issues. I can't get it to misfire, even by lugging the engine under 1200 rpm. I've got a cap/rotor/wire set on order, bought PCV(CCV, little plastic elbow thingys) to fix my blow by, and some new vacuum lines just as maintenance items on this thing. If these don't fix it, does anyone else have any other ideas? I've read about a coolant temp sensor maybe? The fact that it seems to drive ok in 80*F and hotter has me a little confused. Posting this on two separate forums....I'm not looking to parts swap and guess. If you can give me an idea and a possible troubleshooting (or hell steps even!) I would rather do that than throw money away.

So about a week ago my trucks pcv line popped out and got burnt on the manifold. Sigh, but I jerryrigged it together and its held up exceptionally well, until now (I think) So I turned out onto the road and the truck stays in first, cuts my throttle and starts backfiring like crazy, like I had 2 step or something. I quickly pulled off, and turned off the truck. After turning it back on it had no problems, until I got to a stop light, where it just died. I turned it back on and tried to limp it back to school (I was on lunch) and it wanted to die every single stop, it got to the point where I put it in neutral and looked like a dummy revving my truck at a light to keep it on. Well after I made it back, I turned it off, and quickly inspected it. My PCV is still good, everything looks A-OK. I turned it on and it didnt try to die even in gear. I had to go to class which is were I'm at now and I'm at a loss for ideas.

here we go again 86 jeep comanche 93 jeep cherokee 2.5l engine low idle runs good when cold as the idle drops to normal begins to misfire and it gets worse the warmer it gets to the point it dies and starts itself again.... driving down the road at a low rpm runs fine put any type of pressure on the pedal to accelerate it begins to buck and misfire terrible....... drove to work today stopped to turn and the truck died went to start it, and had to hold my foot to the floor to get it to start.... seems like it lacks fuel but pump sending unit resistor and pressure regulator are brand new. i pulled the plugs to see what was going on and all of the plugs had a nice brown tint to them except the furthest back plug which was still sorta white.... list of parts i changed today with no changes.... TPS Distributor temperature sensor Crank sensor fuel pump fuel injector o-rings parts changed recently..... fuel pump ballast resistor fuel pressure regulator spark plugs spark plug wires cap rotor I checked to see if it was the o2 sensor by unplugging and starting the engine and it did not run any better. i am running out of parts to replace and I'm begining to get annoyed at this point.. I'm about to replace every injector and the coil. i checked the ohms rating of each injector and they were all the same across the board..... i checked the primary and secondary of the coil and it was within the ohms ratings.....