Jamesonxj99

So I changed the exhaust manifold on my 99 xj and since then I've had what I believe to be fuel pressure issues. New gaskets no vacuum leaks that I can find. I'm a halfway decent mechanic and I'm lost here. While driving and just giving it gas it misses. Not always, but most of the time. All New ignition components (plugs, wires, cap, rotor, etc..), different tank, pump, filter. Swapped injectors and New o-rings, tb gasket and I've sprayed it all to check for vacuum leaks. Its cuts out so bad while driving that you would think it's out of gas. It says it's running lean but dumps the fuel out. Nothing makes since more than pressure issues but I have no leaks and I have New fuel related parts. Someone please help!

CCKen

If the PCM is getting a lean signal from the O2S' it will add fuel.


Do you have a DTC code you can post?


Do you have a scanner you can see live data? If so, what is the Short Term Fuel Trim (STFT) at idle?


When you changed the exhaust manifold did you disturb the upstream O2S or its wiring?

Jamesonxj99

P0138 and p0171are the two codes. Other is for neutral safety switch. I never messed with the o2 sensors but would the o2 sensors cause it to spit and sputter randomly at certain rpms?? I don't have a scanner either

CCKen

Some things to consider:




P0171-1/1 FUEL SYSTEM LEAN
When Monitored: With the engine running in closed loop mode, the ambient/battery temperature above 20 deg. F and altitude below 8000 ft.
Set Condition: If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored.






POSSIBLE CAUSES
INTERMITTENT CONDITION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR
O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
O2 SENSOR HEATER OPERATION
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM

Jamesonxj99

I swapped out the pcm off of a parts jeep I've got and voila.. Runs good as New! Thank you for all your help