97 XJ rough idle/ CEL ... help!

I've endlessly searched the web and this forum to try and diagnose my issue -- 97 XJ 4.0L AW4 2WD 73K…I’m completely stumped on my CEL/ rough chugging idle (most noticeably when cold, but always comes back when at operating temperature). Didn’t do this before as I drove it for about 2000 miles after purchasing it. I’m 2nd owner. The XJ was in like new condition, but I did a few mods…Borla header & cat back exhaust, Magnaflow cat, all new Mopar sensors – IAC, TPS, MAP, CPS, pre & post oxygen sensors; new ignition coil (Mopar), new Denso distributor wires, Champion 4122 spark plugs, ’00 XJ intake manifold. Has no power when cold, stumbling badly. Get P105 code repeatedly, and then when push it onto freeway get P206 & P305 (cylinder 5 & 6 misfires). Swapped out the oxygen and MAP sensors again just in case they were bad out of the box. I wired in a factory ‘extened idle’ switch and believe I had the positive and negative in the wrong spot and that kicked on a CEL – maybe I had damaged the PCM? No clue. Any experience with issues like this/ causes/ fixes?? Help… I’m down to bad PCM, bad wiring same where in the engine harness, and/or possibly the newer intake manifold? Any advise is appreciated. Thanks

And I checked all the vacuum caps/ lines for cracks and nada. All solid.

All recent repairs and modifications are always good suspects. Have you tested all the OBD sensors, and inspected their wire plugs for corroded/bent/pushed back wire pins ? None of the wire harnesses were re-installed in the incorrect location subjecting them to sharp sheet metal edges or hot exhaust parts ? Did any of the wire harness wire splices fail during the engine work ? You are testing wire continuity between engine sensors and PCM, right ?

Did you install NTK O2 sensors, and not any generic auto parts store brand and definitely not Bosch ?

The P0105 is a good place to start. You should be using your OBD-II Trouble Code scanner with live data display during your diagnostics and troubleshooting. Have you tested the Coolant Temperature Sensor ?


P0105 JEEP - Manifold Absolute Pressure/Barometric Pressure Sensor Circuit

P0105 JEEP Possible Causes
- Faulty Manifold Absolute Pressure (MAP) Sensor
- Manifold Absolute Pressure Sensor harness is open or shorted
- Manifold Absolute Pressure Sensor circuit poor electrical connection
- Faulty Powertrain Control Module (PCM)

You mentioned a lot of new parts(sensors) but Mopar sensors are recommended till we can't buy them anymore. Definitely do a full point to point check on the wiring (resistance/corrosion/insulation break-down/etc)