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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I’ll try to keep this simple, I have a 1993 xj, head gasket blew on the way to work, had a reman head installed because a valve spring broke. Since that was done Iv been having a problem with power loss around 2000 rpm and it’ll backfire sometimes. Iv replaced plugs, plug wires, new cap and rotor, new injectors and fuel pump, mopar tps, new map sensor and iac, hooked up a fuel pressure gauge and am getting 30 psi at at base and when I pull the vacuum line it goes to almost 40 psi, did a compression test on all cylinders and they came back within spec. If I accelerate slowly it runs fine and doesn’t backfire it only happens when I give it gas fast. Before my head blew I was having a problem where my voltage would randomly spike to redline for around 20 seconds and it even blew my headlights when it did it. Voltage on the battery and alt are fine no problems there. My last option seems to be buying a replacement pcm.
oxygen sensor, check spark plug gapping?
my engine light was on, so I changed 1st oxygen sensor, engine light went out , then decided to put new plugs and wires. Now it has a.miss where as b4 the oxygen sensor, it didn't have a miss but would back fire and stall here and there.
So im guessing the plug gapping that stupid me didnt gap
Also the plugs I pulled put were so bad and the #6 didnt even have a gap, so was i running on 5 cyl? lol
All i know now it is running worse with new plugs and wires. wtf
im gonna gap them today see if that stops the missfire.
good luck
Last edited by Justine96xj; 03-15-2021 at 07:19 AM.
oxygen sensor, check spark plug gapping?
my engine light was on, so I changed 1st oxygen sensor, engine light went out , then decided to put new plugs and wires. Now it has a.miss where as b4 the oxygen sensor, it didn't have a miss but would back fire and stall here and there.
So im guessing the plug gapping that stupid me didnt gap
Also the plugs I pulled put were so bad and the #6 didnt even have a gap, so was i running on 5 cyl? lol
All i know now it is running worse with new plugs and wires. wtf
im gonna gap them today see if that stops the missfire.
good luck
One thing you disturbed was the wiring. I can see that you had the harness that crosses over from the firewall to the injector rail bent out of the way. That's an area that flexes a lot anyway. The wires inside the bundle can chaff and wear through, or break from simple fatigue - particularly if you have bad motor mounts. I would open up the wiring loom and inspect that area carefully. Your symptom of dying on mashing the pedal sounds like a bad TPS sensor despite replacing it, so I would grab a meter and measure the signal right at the PCM to make sure it looks right and you don't have any broken wires. Also measure at the TPS connector to make sure the ground, power, and signal look good.
I'd be remiss, if I didn't quote Cruiser54 and suggest cleaning the grounds especially where they all converge to the bolt by the dipstick. The spiking voltage would suggest looking at the wire to the alternator and make sure it's not worn through and hitting ground anywhere (the PCM controls the ground wire for the field coil). If you removed the distributor, you may need to reindex it. Also verify you've got the plug wires in the right place as some of the info out there on the firing order is wrong.
One thing you disturbed was the wiring. I can see that you had the harness that crosses over from the firewall to the injector rail bent out of the way. That's an area that flexes a lot anyway. The wires inside the bundle can chaff and wear through, or break from simple fatigue - particularly if you have bad motor mounts. I would open up the wiring loom and inspect that area carefully. Your symptom of dying on mashing the pedal sounds like a bad TPS sensor despite replacing it, so I would grab a meter and measure the signal right at the PCM to make sure it looks right and you don't have any broken wires. Also measure at the TPS connector to make sure the ground, power, and signal look good.
I'd be remiss, if I didn't quote Cruiser54 and suggest cleaning the grounds especially where they all converge to the bolt by the dipstick. The spiking voltage would suggest looking at the wire to the alternator and make sure it's not worn through and hitting ground anywhere (the PCM controls the ground wire for the field coil). If you removed the distributor, you may need to reindex it. Also verify you've got the plug wires in the right place as some of the info out there on the firing order is wrong.
Iv definitely been considering digging through that wire loom, it’s the only thing that would make sense at this point. I did pull and clean all grounds and checked for good solid ground with my multimeter.
so, it might not be at all related, but do a compression check. I have been having a nearly identical issue on my 89, renix, won't rev over 2000rpm. looks like I have an exhaust valve stuck open, so going to be doing a head on mine here soon.
so, it might not be at all related, but do a compression check. I have been having a nearly identical issue on my 89, renix, won't rev over 2000rpm. looks like I have an exhaust valve stuck open, so going to be doing a head on mine here soon.
that was actually one of the first things I did when I started having issues, thankfully compression came back at perfect levels
03-14-2021, 06:06 PM
Weird misfire and loss of power around 2000 rpm
