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I was going to suggest the CPS like you listed on your next steps, Personally most people that replace it and go through anything but Mopar's does crap out quickly.
Troubleshooting Help Possible Fuel/Timing/sensor problem
Problem fixed.....Fuel Pump!
I've been chasing a problem for a while. Here's the details.
-94 xj 4.0 5spd 4.56 gears 210k miles
-symptoms: Runs fine until operating temp. At op temp consistently bogs at apprx 3-3.5k rpm (25 mph) in second gear with throttle wide open. Jeep pushes through bogging and eventual acclerates normally. Occasionally problem gets very bad and vehicle comes to a stop without dieing. Goes nowhere with pedal to the floor but if I turn it off and restart everything is 'fine' again for a few minutes. At first it seemed like gas was not getting to engine but now wondering if injectors are acually opening too much and problem is fuel too rich instead of lean (really not sure about this).
Attempted fixes and diagnostic
-No engine codes.
-Fuel pump (car had set for long time and I know the gas was bad), Fuel Filter, drop and clean gas tank, another fuel pump. Fuel treatment. No Luck
-Plugs & wires for the heck of it. No Luck
-Tested TPS. Showed 3.7v at open throttle so replaced. No Luck. Guessing bad test reading was operator error.
-Replaced fuel regulator. No Luck
-Pulled injectors. Cleaned tested w/12v and all clicked open each sounded the same.
-Waited for problem to occur. Disconnected O2 senser and became a little worse. Was hoping that since problem only happens at op temp that unplugging O2 may trigger open loop reading. Didn't run w/out o2 sensor long. Just enough to see that it only made minimal difference.
-Have not truly tested O2 sensor
-Inspected hoses to MAP
Possible next Steps
-Test O2
-Test MAP
-Test CPS (Crank). CPS on there now is from Autozone and was the solution a couple yrs ago. I've heard Auto Zone CPS can crap out early.
-Maybe Fuel Filter again. Filter has not been replaced since fuel treatment was run but since problem is only at op temp don't see how fuel filter could be a problem.
-Burn Jeep or take to mechanic.
Thanks to anybody who actually took the time to read all of that.
Last edited by CpnJack; 09-05-2010 at 09:31 PM.
I was going to suggest the CPS like you listed on your next steps, Personally most people that replace it and go through anything but Mopar's does crap out quickly.
retest that tps. if voltages are wrong it can be in the wiring or computer, not just the sensor itself.
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Thanks for the ideas. I'll give TPS and CPS a look this week or next weekend. Ran out of time today and didn't even mow the lawn. Still collecting thoughts if anybody else has suggestions.
Well, have a huge laundry list of things I've tried. Finally took it to a shop where it just sat (they didn't even pop the hood once) in their yard for 3.5 weeks before I gave up on them and took the xj back. Took it to the dealership. They worked on it for 4 straight days and finally called me tonight to say they gave up. Not really sure where to go from here. Thinking I'll try a jy PCM. If that doesn't work it might be time to strip the lift and axels off and start looking for another ride.
Coil, CPS.
In no particular order.
Since the original post I've done
CPS
O2
Hacked hole in front of Cat. in case it was clogged
IAC
Coolant Temp Sensor in thermostat housing
Have not checked coil. I've been focused on sensors and PCM because it runs fine for a minute or two when engine is first turned on (thinking default codes are working so problem seems related to when PCM starts getting data from sensors). I'll check the coil though, appreciate the suggestion.
That can be pretty exhausting and not to mention frustrating. My guess would have been cps or cat, mine had the same issues and those were the culprits. I would check the PCM also. Hope you get it figured out
Plugged in a PCM from the junk yard and have the exact same problem. In case anybody was wondering, a PCM from xj with auto transmission works with a standard transmission. I'm almost 100% sure the reverse swap does not work though.
Going to test the coil this weekend, hope sceep is right. Also, jeep is now sputtering on right hand turns. Gas is over half tank. Going to take another look at the fuel pump and wiring.
Anybody know the continuity specs on coil for 94 xj (part 5234610). Did some searching and only found one source that says primary is b/w .95 and 1.2 ohms. Primary tested at 1.3 ohms. Problem is autozone says specs are .75 to 1.5 ohms. Not really worried about secondary because it tested well within range at 12500. I'm going to keep looking but appreciate any help.
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