I have a stubborn “LEAN MIS-FIRE” problem with my 1996 MY 4.0L AJ16.
Even after replacing too many parts:
All O2 sensors and harness connectors (O2 sensor orientation test completed with IDS/WDS)
Throttle Position Switch (TPS reset using IDS/WDS)
MAF (I have 2 new aftermarket and 2 used)
coils, and harness connectors with shrink wrap over all failing insulationPlugs (Champion RC12YC)
Fuel filter, and fuel pressure regulator (pressure is good), Air filter
Rebuilt fuel injectors (that looked different, so I rebuilt the original injectors, flushed them and reinstalled the originals)
Exhaust manifolds (they were cracked), and front catalytic converter, EGR valve
(I’m sure there were more)
I still have not been able to fix this, and could really use some expert help.
Symptom 1: repeated MIL codes
P0171, ADAPTIVE FUEL, Combustion too LEAN, Bank 1
P1138, HO2 sense circuit lack of “swing”, Bank 1, Sensor 2 Sense circuit indicates lean combustion (No HO2S response)
P1315, Persistent misfire (one cylinder identified and injector switched off)
P1314, Misfire Rate catalyst damage, Bank 2
P0300, Random misfire detected
Symptom 2: Champion Spark plugs look VERY LEAN (bright white)
Symptom 3: Low voltage on O2 sensor “C” (B1S1)
Here are the O2 sensor voltage traces (using IDS 118.5/WDS with a genuine VCM).
Sensor A= Bank 1, Sensor 2 (downstream)
Sensor B= Bank 2, Sensor 2 (downstream)
Sensor C= Bank 1, Sensor 1 (upstream)
Sensor D= Bank 2, Sensor 1 (upstream)
I have changed all 4 O2 sensors, and the Bank 1 Sensor 1 O2 sensor (sensor “C”) twice, and still get the same results.
I have checked ALL the O2 sensor wiring and it is OK.
When I turn the engine OFF, key ON, I can watch the voltage rise back to 5v.
I believe this O2 sensor problem is causing my AMFR and FMFR to drift out of spec.
I found a way to “hack” reset the AMFR using IDS/WDS: Vehicle Configuration - Set-up and configuration - Engine and transmission - Fuel trim set up. I don’t actually have a smog machine, but if I lie and say the “measured” carbon monoxide level is 05.% or 1% or 1.5%, WDS updates the ECU at least a little (engine runs rough during change)…keep repeating the process until you get the PASSED screen and the level is right. I was able to change my AMFR from -12.5kg/hr all the way to 531 g/hr. Spec according to Bulletin Number 18-53 and 05-1-31 is AMFR -4.2 to +2.8 kg/hr. The problem is, even after I get the AMFR adjusted to spec, it drifts right out again.
Is the O2 sensor telling the truth? Is that really is the O2 level? what is going on here?
I also wanted to re-set the FMFR per Bulletin Number 18-53 and 05-1-31 (apparently, fixing the initial AMFR problem WONT be enough; you must also re-establish the proper AMFR and FMFR for the ECU…it can’t do it without your invention)
After setting up the 4 traces, per the bulletins, the signal for the Calculated engine Load Value “CLV” reading keeps dropping out (error messages that I can’t look up). The transmission had started shifting very badly, so I replaced the VSS. Shifts are better, but the CLV signal is still dropping out. When I check ONLY the CLV, it seems fine.
My smog is past due by 1 1/2 years, and the great state of California could tow my car away to ‘save the world’ if they catch me driving it (so I don’t drive it).