Blindtheft
NAXJA Forum User
- Location
- United States
Ok, I give. I've been banging my head against the wall on this for quite a while now and could use some help troubleshooting. If you're able to assist, it'd be greatly appreciated. I have a 4.7L stroker (Pottenger - TUPY head) with 18,000 miles in my '01 XJ.
Symptoms:
CEL has been intermittent for several months, increasing to just about every trip now. All cylinders have thrown codes along with the general misfire (P0300), but it's typically 4 on its own or with others. Cylinder 3 is there as often as not also. The others show up, but far less frequently. No backfires or stutters, although the computer has put it into limp mode twice. I'd call the idle slightly rough.
Does not matter if the engine is cold, hot, or has been sitting for a couple of days. Usually happens pretty quick - maybe 2-5 minutes after starting. Seems to be getting worse lately as the CEL has now started blinking occasionally the past couple of weeks.
What I've done so far (pretty much all of this needed doing anyway at 150,000 miles, so I've considered it maintenance as well as troubleshooting):
Changed plugs. Old plugs looked fine.
Cleaned all grounds and swapped in solid heavy gauge cables.
Changed oil. Oil looks fine. Went to 5W 20 in case lifters were being pumped up by cold oil.
Went to 4 hole injectors.
Swapped injector 4 with injector from cylinder 1.
Inspected all wiring going to/from the injectors. Found cracked and brittle wires on a couple of injector plugs from what looked to be heat. Rewired those with new pigtails. (I could dig deeper into the wiring harness I suppose - there might be a short buried somewhere, but I did give it a once over.)
Cleaned idle air control valve.
Replaced throttle position sensor.
Replaced crankshaft position sensor (I didn't think this was too bad despite all the posts to the contrary).
Replaced coil rail with Viper coil.
Pressure test - looked good.
Banged on cats and pre-cats. No rocks.
None of this has had any effect whatsoever.
I've read a ton of threads on misfires as well as the FSM. My situation doesn't look like heat soak. As far as I can tell, this leaves me with: i) replacing O2 sensors, ii) the camshaft position sensor (toothpick test), and iii) leakdown test.
Where else should I go with this? Any advice?
Symptoms:
CEL has been intermittent for several months, increasing to just about every trip now. All cylinders have thrown codes along with the general misfire (P0300), but it's typically 4 on its own or with others. Cylinder 3 is there as often as not also. The others show up, but far less frequently. No backfires or stutters, although the computer has put it into limp mode twice. I'd call the idle slightly rough.
Does not matter if the engine is cold, hot, or has been sitting for a couple of days. Usually happens pretty quick - maybe 2-5 minutes after starting. Seems to be getting worse lately as the CEL has now started blinking occasionally the past couple of weeks.
What I've done so far (pretty much all of this needed doing anyway at 150,000 miles, so I've considered it maintenance as well as troubleshooting):
Changed plugs. Old plugs looked fine.
Cleaned all grounds and swapped in solid heavy gauge cables.
Changed oil. Oil looks fine. Went to 5W 20 in case lifters were being pumped up by cold oil.
Went to 4 hole injectors.
Swapped injector 4 with injector from cylinder 1.
Inspected all wiring going to/from the injectors. Found cracked and brittle wires on a couple of injector plugs from what looked to be heat. Rewired those with new pigtails. (I could dig deeper into the wiring harness I suppose - there might be a short buried somewhere, but I did give it a once over.)
Cleaned idle air control valve.
Replaced throttle position sensor.
Replaced crankshaft position sensor (I didn't think this was too bad despite all the posts to the contrary).
Replaced coil rail with Viper coil.
Pressure test - looked good.
Banged on cats and pre-cats. No rocks.
None of this has had any effect whatsoever.
I've read a ton of threads on misfires as well as the FSM. My situation doesn't look like heat soak. As far as I can tell, this leaves me with: i) replacing O2 sensors, ii) the camshaft position sensor (toothpick test), and iii) leakdown test.
Where else should I go with this? Any advice?
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