NEED HELP!! 01 XJ skip/missfire.

bannerp

bannerp

Well-Known Member
Joined
Dec 4, 2011
Location
Newland NC
Jeep belongs to a coworker. 2001 XJ 4.0 AW4 4WD 123k. We have checked and or replaced the following with either new parts or known good used ones. We will start from the beginning, Jeep had a starting problem, had fuel pressure, injector pulse, spark. Sounded like it had low compression. Preformed compression test wet and dry. cylinders 1 thru 3 were low. Checked for jumped time, checked for bent/ broken push rods and lifters. TURNED OUT TO BE WATER IN FUEL. and the rings were washed down causing low compression.

After draining the tank jeep developed a skip on cylinders 3&4. replaced spark plugs, Coil with a known good used 1, Cam sensor, Crank sensor, Removed exhaust system to check for bad convertors, Checked running fuel pressure, replaced complete injector rail with known good 1. Checked spark, Injector pulse, compression test (100-130psi Dry) preformed cylinder leak down test. ALL THIS CHECKS OUT! Only codes are P0303 and 0304. We are stumped everything says it should run perfect. MY ? is has anyone ever seen a connecting rod warp or something of that nature? THE jeep was spun over repeatedly with the bad gas, could the water have bent a rod? Only reason I ask is I have seen this on ford 3.8's any help would be greatly appreciated!
 
Also forgot to mention we have preformed a B&G injection clean thru the fuel rail so intake valves and injectors should be clean.
 
Based on what you have posted, I would do the following.
Swap injectors around an see if the miss follows the injectors. Water causes rust, rust clogs injectors. Doesn't matter if you have pressure and pulse. Without flow you will have a miss.
Also, the injector wires are known to fatigue over time and cause poor connection issues. Wiggle the wires at the connector and see if it clears up at all.
 
We have swapped the complete injector rail with a known good 1. He also has a WJ also and it runs fine. Haven't preformed a wiggle test cause it only skips under load not at idle. May try to powerbrake it and load the engine to see.
 
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