Long time lurker, first time poster.
I bought a 3.6 JKU from the auction yards in Australia a few months ago and have pretty much torn my hair out battling consistent P0300 issues. Its left myself, a mechanic friend [very experienced race engine builder], two other mechanics [40yrs+ experience and run their own machine shop] and a renown diagnostic tester absolutely stumped. Im at the point where i need a new perspective or a new set of eyes over it because everything weve tried so far has resulted in the issue coming back with a vengeance - the longest ive gotten out of it without it throwing the dreaded code and misfiring was 5 days recently. I have pretty much trawled the depths of google looking for answers and am still none the wiser as to what is causing this.
Symptoms; pronounced misfire and driveability issues up to 3000rpm, has no issue revving to redline in gear. Extended idling or cruise amplifies and makes the misfire worse. Have confirmed via JScan, the diagnostic tester and the condition of the spark plugs it is definitely running richer on Bank 2. For some reason, the fuel trims are showing +30% on bank two - we just dont know why.
So far I have done the following in the hunt to remove the ghost from the machine:
-Repaired wiring to Bank 2 Sensor 1 Oxygen sensor
-Replaced PCV Valve on rocker cover [genuine MOPAR] and cleaned inline PCV Valve
-Replaced 4x o2 Sensors with genuine NTK
-Replaced 6x Injectors with Genuine BOSCH
-Replaced 6x ignition coils with genuine NTK
-Replaced 6x Spark plugs with genuine NGK
-Replaced air temp, coolant temp, and map sensors - Genuine MOPAR
-Replaced upper inlet manifold [genuine MOPAR] and checked lower for cracks and straightness, new gaskets. Complete intake smoke tested
-Replaced 4x VVT Solenoids
-Replaced 2x Cam Syn Sensors
-Replaced throttle body gasket
-Replaced thermostat and housing with genuine MAHLE
-Repaired wiring to Bank 2 Sensor 2 oxygen sensor
-Compression test; all cylinders within 10psi of each other [average 150psi]
-Cat temps have been checked both via JScan and infrared thermometer; within 10deg celcius
The most recent discovery was the insulation was missing from the bank 2 sensor 2 o2 wiring near the connection. This was repaired and the car was flawless for 500km before it returned again. At this point, and on the balance of everything we looked at, we do not believe the issue is mechanical [worn cam, rockers, burnt valve] as the compression tests dont reflect this nor do mechanical problems just disappear. Like i said, when its going, its going fine. The issue is isolated to bank 2 according to the scanner and the condition of the spark plugs on that bank. The question is WHY.
On the balance of everything ive seen so far, I suspect there is an issue with the wiring, most likely in the oxygen sensor circuit based off the condition of what ive found there previous and the persistant overfuelling. Does anyone have a wiring diagram for the o2 sensor circuit and a pin out to PCM/resistance values? The other thought is it may be the bank 2 injector circuit causing the problem. If its not the wiring, its looking likely that its PCM and I dont want to throw money on that until Ive ruled everything else out.
Anything ive missed? Its driving me crazy at the moment and I really need this thing to run. Its currently the rather sour icing on a pretty sh*tty cake [divorce, redundancy and now the Jeep]
Thanks in advance
Nick
I bought a 3.6 JKU from the auction yards in Australia a few months ago and have pretty much torn my hair out battling consistent P0300 issues. Its left myself, a mechanic friend [very experienced race engine builder], two other mechanics [40yrs+ experience and run their own machine shop] and a renown diagnostic tester absolutely stumped. Im at the point where i need a new perspective or a new set of eyes over it because everything weve tried so far has resulted in the issue coming back with a vengeance - the longest ive gotten out of it without it throwing the dreaded code and misfiring was 5 days recently. I have pretty much trawled the depths of google looking for answers and am still none the wiser as to what is causing this.
Symptoms; pronounced misfire and driveability issues up to 3000rpm, has no issue revving to redline in gear. Extended idling or cruise amplifies and makes the misfire worse. Have confirmed via JScan, the diagnostic tester and the condition of the spark plugs it is definitely running richer on Bank 2. For some reason, the fuel trims are showing +30% on bank two - we just dont know why.
So far I have done the following in the hunt to remove the ghost from the machine:
-Repaired wiring to Bank 2 Sensor 1 Oxygen sensor
-Replaced PCV Valve on rocker cover [genuine MOPAR] and cleaned inline PCV Valve
-Replaced 4x o2 Sensors with genuine NTK
-Replaced 6x Injectors with Genuine BOSCH
-Replaced 6x ignition coils with genuine NTK
-Replaced 6x Spark plugs with genuine NGK
-Replaced air temp, coolant temp, and map sensors - Genuine MOPAR
-Replaced upper inlet manifold [genuine MOPAR] and checked lower for cracks and straightness, new gaskets. Complete intake smoke tested
-Replaced 4x VVT Solenoids
-Replaced 2x Cam Syn Sensors
-Replaced throttle body gasket
-Replaced thermostat and housing with genuine MAHLE
-Repaired wiring to Bank 2 Sensor 2 oxygen sensor
-Compression test; all cylinders within 10psi of each other [average 150psi]
-Cat temps have been checked both via JScan and infrared thermometer; within 10deg celcius
The most recent discovery was the insulation was missing from the bank 2 sensor 2 o2 wiring near the connection. This was repaired and the car was flawless for 500km before it returned again. At this point, and on the balance of everything we looked at, we do not believe the issue is mechanical [worn cam, rockers, burnt valve] as the compression tests dont reflect this nor do mechanical problems just disappear. Like i said, when its going, its going fine. The issue is isolated to bank 2 according to the scanner and the condition of the spark plugs on that bank. The question is WHY.
On the balance of everything ive seen so far, I suspect there is an issue with the wiring, most likely in the oxygen sensor circuit based off the condition of what ive found there previous and the persistant overfuelling. Does anyone have a wiring diagram for the o2 sensor circuit and a pin out to PCM/resistance values? The other thought is it may be the bank 2 injector circuit causing the problem. If its not the wiring, its looking likely that its PCM and I dont want to throw money on that until Ive ruled everything else out.
Anything ive missed? Its driving me crazy at the moment and I really need this thing to run. Its currently the rather sour icing on a pretty sh*tty cake [divorce, redundancy and now the Jeep]
Thanks in advance
Nick