WJgospelgauge
NAXJA Forum User
Crossposting from NAGCA for help if possible:
Hi All,
I have a 2004 WJ with a new used 4.0 that I've dropped in out of a 2006 TJ after a catastrophic failure on the original motor. I have been chasing a weird cylinder 1 misfire since the motor went in.
Symptoms:
When the engine is started, it runs perfectly until warm, then starts stumbling at idle and going lean on the STFT for B1. Trims go positive when RPMs are above 1k, and it pulls fine under load, but at idle it goes lean and stumbles like a son of a gun. Things that have been done to rectify:
New Champion plugs
New Standard Products Coil (x2, tried another in case there was a failure in the first replacement as I've had that before)
New TPS
Cleaned IAC and realized it was broken, so I replaced that.
Chased all the vacuum leaks I could find and repaired, including a new throttle body gasket.
Swapped Injector 1 and 2, no change.
New Fuel Injector O-rings, no change.
Repaired the Coil plug as the plug itself was bad with the Dorman kit. Soldered and heat shrinked in place. It ran fine before this outside of the misfire, but I figured it wouldn't hurt to attempt a repair.
Noid light on injector plugs, it blinks when running, however occasionally on cylinder 6 it does nothing (more on that later)
Hot Compression test:
196 PSI Cylinder 1
195 PSI Cylinder 2
190 PSI Cylinder 3
194 PSI Cylinder 4
194 PSI Cylinder 5
195 PSI Cylinder 6
I have not performed a cold compression test yet, but I will do so if deemed prudent.
Exhaust gas test in cooling system, no sign of exhaust gasses.
Seafoam through throttle body to see if perhaps it's a gunked up valve since the engine sat for ~4 years before being installed in my Jeep.
During engine install, a new B2S2 O2 sensor was installed (NAPA) and a new CPS (NAPA) as well. I have no issues starting the engine, hot or cold, and it does not stall so I'm doubtful that it is a CPS issue. 02 Voltages are responsive to throttle input and load changes, so I also am doubtful that it is an 02 sensor, however I do not have a Picoscope to triple check it.
My supposition at this point is that I either have a bad wiring harness, a burnt valve (Is this possible with the hot compression numbers shown above?), bad valve spring, or bad rings (Although I'd imagine that with a valvetrain or piston ring issue I wouldn't be able to achieve the compression that I'm achieving? Noid light flashes for all 6 injectors, however occasionally it does NOT flash on injector 6. I'm not sure if that's user error in using the noid light given the location of injector 6 plug or an actual issue. Would a misfire on Cylinder 6 accidentally trigger a P0301 for Cylinder 1 by chance? I do not notice a change in the engine stumble when unplugging ANY of the injector harnesses, so I'm wondering if it's just a low voltage or intermittent short to ground issue?
I'm stumped, as I want to make this thing run correctly but I can't seem to figure this out. Thoughts? Help?
Thanks in advance!
Hi All,
I have a 2004 WJ with a new used 4.0 that I've dropped in out of a 2006 TJ after a catastrophic failure on the original motor. I have been chasing a weird cylinder 1 misfire since the motor went in.
Symptoms:
When the engine is started, it runs perfectly until warm, then starts stumbling at idle and going lean on the STFT for B1. Trims go positive when RPMs are above 1k, and it pulls fine under load, but at idle it goes lean and stumbles like a son of a gun. Things that have been done to rectify:
New Champion plugs
New Standard Products Coil (x2, tried another in case there was a failure in the first replacement as I've had that before)
New TPS
Cleaned IAC and realized it was broken, so I replaced that.
Chased all the vacuum leaks I could find and repaired, including a new throttle body gasket.
Swapped Injector 1 and 2, no change.
New Fuel Injector O-rings, no change.
Repaired the Coil plug as the plug itself was bad with the Dorman kit. Soldered and heat shrinked in place. It ran fine before this outside of the misfire, but I figured it wouldn't hurt to attempt a repair.
Noid light on injector plugs, it blinks when running, however occasionally on cylinder 6 it does nothing (more on that later)
Hot Compression test:
196 PSI Cylinder 1
195 PSI Cylinder 2
190 PSI Cylinder 3
194 PSI Cylinder 4
194 PSI Cylinder 5
195 PSI Cylinder 6
I have not performed a cold compression test yet, but I will do so if deemed prudent.
Exhaust gas test in cooling system, no sign of exhaust gasses.
Seafoam through throttle body to see if perhaps it's a gunked up valve since the engine sat for ~4 years before being installed in my Jeep.
During engine install, a new B2S2 O2 sensor was installed (NAPA) and a new CPS (NAPA) as well. I have no issues starting the engine, hot or cold, and it does not stall so I'm doubtful that it is a CPS issue. 02 Voltages are responsive to throttle input and load changes, so I also am doubtful that it is an 02 sensor, however I do not have a Picoscope to triple check it.
My supposition at this point is that I either have a bad wiring harness, a burnt valve (Is this possible with the hot compression numbers shown above?), bad valve spring, or bad rings (Although I'd imagine that with a valvetrain or piston ring issue I wouldn't be able to achieve the compression that I'm achieving? Noid light flashes for all 6 injectors, however occasionally it does NOT flash on injector 6. I'm not sure if that's user error in using the noid light given the location of injector 6 plug or an actual issue. Would a misfire on Cylinder 6 accidentally trigger a P0301 for Cylinder 1 by chance? I do not notice a change in the engine stumble when unplugging ANY of the injector harnesses, so I'm wondering if it's just a low voltage or intermittent short to ground issue?
I'm stumped, as I want to make this thing run correctly but I can't seem to figure this out. Thoughts? Help?
Thanks in advance!
