Hi,
2004 Lincoln Navigator 5.4 2WD, 163K miles.
Under high rpm / load (in 2nd gear at 60, accelerating), I'm seeing up to ~52% positive STFT on bank 1 (passenger side). Other symptoms: the engine will not produce full power for 3-4 seconds when stepped on at 4K RPM but then snap back into full power delivery. The one-sided high STFT numbers remain.
At idle and under "easy" driving conditions, my fuel trims and O2 voltages look normal. This is important to mention because I've already spent considerable amount effort eliminating vacuum leaks. Since the intake plenum vacuum pressure is highest at idle, it should also show in the numbers but all 4 fuel trim values are well below +-10% at idle.
Yesterday, I got a P2195 code for bank 1 after an engine flush and oil change and some driving, after a 20 minute stop w engine off. Previously, I've recorded 2 instances of the same code and after 2 O2 sensor failures believe there's a connection here. I'd replaced all 4 with OEM units and didn't get another code for 4+ months.
For reference, here's everything else that's been replaced / fixed so far: EGR valve, DPFE sensor (EGR system is now working properly), MAF sensor, intake manifold gasket, PCV Valve, numerous vacuum hoses. Timing chains & guides, melling high pressure oil pump, coils, plugs, injectors (+1 injector connector that was burnt, all motorcraft parts), fuel pressure regulator, fuel filter. Compression was even and strong across all cylinders when last measured.
Remaining areas for consideration:
- Brake master cylinder was leaking when I bought the vehicle. Replaced it. These can leak into the booster and damage it. There's rust on the outside from the leak on the booster and a consistent weird popping noise at the brake pedal after the vehicle was parked but I'm not seeing signs of a vacuum leaking brake booster in terms of brake performance. The above mentioned sensor values at idle also don't point in this direction as the culprit.
- Passenger side exhaust manifold leak: I'm not hearing any leaks but don't want to rule this out until I've heard from more experienced folks here that these are always audible or not. What seems odd is the "snap"-like correction in the power delivery mentioned above. Not sure how that fits a manifold leak as the source.
- A problem with the ECM or injector wiring. A short in one of the injector wires could mess up fuel delivery. A P2195 can indicate a leaking injector so I'm currently leaning towards that.
Anything else glaring that I'm overlooking? - Has anyone else experienced similar symptoms? How do I best test the injector wiring circuits for shorts or other issues? (Visually, everything looks find, I also cleaned the connectors)
Thanks!
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