1999 xj aw-4 165k 3" lift, 2mm bored-over TB, 2.5" exhaust header-back, previously i had no catalytic converter until i needed to pass emissions about 4mo ago. these mods have been on the vehicle for years and never had a problem. but the problem did arise after making adjustments for emissions but was not corrected with adding a magnaflow 3-way cat.
i have read every thread/post/link and spent countless hours studying and testing straight out of the FSM. but i just cant think anymore and need some help. i will try to give as much info without side-tracking, just ask if i forgot something. thanks in advance for any advice .
THE PROBLEM: the hotter the motor, the harder time it has idling and even running. i think. i drive to work when its cool and it would be fine. 10hrs later and 20-30 degree temp change outside, it doesnt want to idle smooth. it will knock, buck, lurch, and most times stall. every now and then it seems it works thru it and starts running fine again. but the stalling has been getting worse (and the temps here are getting 90+ everyday). but then it started throwing codes/CELs randomly (maybe 2% of the time this happens) for running lean. runs ok on the road/highway if you can get it there, but as soon as the rpms go under 1500 it will die and not restart for long time. leaving me stranded and sitting in intersections. when it does start, its rough, starter fluid evens it out but touching the throttle will bog it down worse. this makes me think IAC or TPS, but they have both been changed out.
THE WORK: i started with the basics. checking vacuum lines for leaks, swapping relays and checking fuses, testing and replacing sensors, replacing plugs and cleaning grounds.
MAP, TPS, CPS, IAC, pickup coil, and both O2 sensors all tested good, swapped several other known working ones with no change. dist cap, rotor, wires, ign coil, fuel pump, fuel filter are about 18mo. head gasket, coolant flush, thermostat, coolant sensor, champion plugs last weekend. ran great for a few days. but then i added BG44K and got a full tank of 87 (which is usually what i run) and now it will barely stay running. and you can clearly tell by the plugs that it is running way lean, even though i rarely get a code for it.
THE BAD: found that the wiring harness plugs for injectors #1 and #2 were swapped. corrected issue, reset computer, slight change but not fixed. got a brand new fuel pressure test gauge and hooked it up. fuel pressure fluctuates between 15-30psi, normally evening out around 24psi. it stumble and died and i just watched the gauge. within 4min of stalling, fuel pressure climbed to a peak of 48psi, and then started dropping fast with 0psi by the 25min. fuel pump override did pass the capacity/volume test by pumping 1qt in under 30sec. so its pumping, no pressure though, so i assume the fuel regulator. but then out of no where it starts running fine with no issues. and there is no difference in fuel pressure when it does run good. would that mean my brand new gauge is outta whack or do i have a leaky injector? it does seem that my oil is too clean and thin after only a week since new oil change. i am think that a leaking injector is my problems but looking for some more opinions. i should mention that when my fuel pump was replaced ~18mo i believe it was an airtex which ive heard is poor quality. regulator was not replaced, just the pump and strainers. and when i pulled the fuel pump to investigate, things did not look like they were assembled right, and i am missing the larger strainer altogether.
a lot of these issues started when i was trying to pass emissions. i believe that chemicals and cleaners may have cause some issues. ironically, even such things as BG44K made it run worse. do i need to investigate and troubleshoot more, or does all this point to a fuel pump/regulator/injector issue? and if so, which way should i go looking for my problem? or should i go back to testing sensors like the IAC and TPS?
thank you again for reading and for offering any real advice off the info i have given. again, please feel free to ask more questions that i may have forgot :cheers:
i have read every thread/post/link and spent countless hours studying and testing straight out of the FSM. but i just cant think anymore and need some help. i will try to give as much info without side-tracking, just ask if i forgot something. thanks in advance for any advice .
THE PROBLEM: the hotter the motor, the harder time it has idling and even running. i think. i drive to work when its cool and it would be fine. 10hrs later and 20-30 degree temp change outside, it doesnt want to idle smooth. it will knock, buck, lurch, and most times stall. every now and then it seems it works thru it and starts running fine again. but the stalling has been getting worse (and the temps here are getting 90+ everyday). but then it started throwing codes/CELs randomly (maybe 2% of the time this happens) for running lean. runs ok on the road/highway if you can get it there, but as soon as the rpms go under 1500 it will die and not restart for long time. leaving me stranded and sitting in intersections. when it does start, its rough, starter fluid evens it out but touching the throttle will bog it down worse. this makes me think IAC or TPS, but they have both been changed out.
THE WORK: i started with the basics. checking vacuum lines for leaks, swapping relays and checking fuses, testing and replacing sensors, replacing plugs and cleaning grounds.
MAP, TPS, CPS, IAC, pickup coil, and both O2 sensors all tested good, swapped several other known working ones with no change. dist cap, rotor, wires, ign coil, fuel pump, fuel filter are about 18mo. head gasket, coolant flush, thermostat, coolant sensor, champion plugs last weekend. ran great for a few days. but then i added BG44K and got a full tank of 87 (which is usually what i run) and now it will barely stay running. and you can clearly tell by the plugs that it is running way lean, even though i rarely get a code for it.
THE BAD: found that the wiring harness plugs for injectors #1 and #2 were swapped. corrected issue, reset computer, slight change but not fixed. got a brand new fuel pressure test gauge and hooked it up. fuel pressure fluctuates between 15-30psi, normally evening out around 24psi. it stumble and died and i just watched the gauge. within 4min of stalling, fuel pressure climbed to a peak of 48psi, and then started dropping fast with 0psi by the 25min. fuel pump override did pass the capacity/volume test by pumping 1qt in under 30sec. so its pumping, no pressure though, so i assume the fuel regulator. but then out of no where it starts running fine with no issues. and there is no difference in fuel pressure when it does run good. would that mean my brand new gauge is outta whack or do i have a leaky injector? it does seem that my oil is too clean and thin after only a week since new oil change. i am think that a leaking injector is my problems but looking for some more opinions. i should mention that when my fuel pump was replaced ~18mo i believe it was an airtex which ive heard is poor quality. regulator was not replaced, just the pump and strainers. and when i pulled the fuel pump to investigate, things did not look like they were assembled right, and i am missing the larger strainer altogether.
a lot of these issues started when i was trying to pass emissions. i believe that chemicals and cleaners may have cause some issues. ironically, even such things as BG44K made it run worse. do i need to investigate and troubleshoot more, or does all this point to a fuel pump/regulator/injector issue? and if so, which way should i go looking for my problem? or should i go back to testing sensors like the IAC and TPS?
thank you again for reading and for offering any real advice off the info i have given. again, please feel free to ask more questions that i may have forgot :cheers:
