2002 F-250 5.4l 4x4

Im getting a P0171 code only, with strong fuel smell. No P0174 code. So it has to be something effecting just the one bank? Sprayed engine with starting fluid, no charge in idle. Replaced upstream O2 sensor, no change.

Truck was running fine, and then just started this all at once.

Any ideas?

Thanks.

 

Not necessarily. It might only have set a bank one code so far. You'd need to go in and look at the bank 2 LTFT and see if it's skewed positive. It might be close to, but not over, the threshold to set a DTC. You won't know unless you actually LOOK at that values.

O2 sensors do not cause this symptom, they report the condition. Therefore, you shot the messenger.

Your symptom is almost always caused by a large vacuum leak and is most usually caused by the PCV valve's plumbing.

 

Sorry for the delay. Been very busy and the truck has mostly just sat for the past few months.

I get that the O2 sensor is just reading the condition, but it is possible that it was reading it incorrectly and causing a rich condition, so don't act like that was completely misguided.

There are no vacuum leaks on this engine.
Also, it runs fine for 30-45 seconds on cold start up then just gets really bogged down. So what happens on a cold start and turns off or makes an adjustment after a short time?

I've also unplugged fuel injectors and coil packs, on the drivers side, and it causes no change it how it is running. I Don't think that any of the drivers side cylinders are firing.

About to just set the truck on fire and see if that helps.

 

I can't imagine the engine even runs with half of the cylinders not firing. I also can't think of anything that would isolate just one bank.
I agree the most common issue is a vacuum leak for either of those codes, especially the pcv elbow, but I would bet a COP or two just not firing. Bad boot or rusted or Coil line.
I'd pull the COP's and look for moisture in one of the plug holes in case a manifold coolant leak too.

 

This was my initial reaction as well. I can unplug all 4 of the coil packs at the same time with no change in how the engine runs, but if I unplug one on the other bank, it starts to get really bad (as expected).

I did replace to of the coil packs on the drivers side, but it didn't seem to make a difference.

Also with the engine running strong for the first few seconds, it leads me to believe the coil packs are good. They wouldn't be ok for 30 secs cold and then stop. I'm pretty certain that because of the way it's acting (like flipping a switch after 30-45 seconds) that's its electrical, or a sensor or adjuster that's changes states after a cold start, and screws everything up.

 

It could also be a fuel delivery problem such as a clogged filter, although the you'd expect it to affect both sides, bad pump, or a bad regulator, fouling up fuel pressure for the injectors on the one bank?
With new COP's on the one side, you'd expect them to fire unless a fuel issue.