Bank 1 lean P0171

blackburb · Sep 9, 2019

I haven't had a chance to look into this yet, but I wanted to get some thoughts. Seems to me if it's only bank 1 and not both, it's probably not fuel filter or fpr related correct? I'm thinking I should be looking for a bad injector. Runs like it's misfiring, but no blinking light or misfire code.

Rich_007 · Sep 10, 2019

I went thru this last year with my 01 5.4. If I remember right its a lean bank 1 and the code for bank 2 might not be far behind. Lots of things can cause this. Hopefully its just unmetered air getting in down stream from the maf, so its running rough cause the mixture is based on what the maf says which is bad info if you are sucking air in afterwards. Check all your hoses and get it smoke tested to see if there is a leak. I think that's the cheapest way to start before you start buying injectors. Good Luck.

blackburb · Sep 12, 2019

So as it turns out, when I was working on the number 4 spark plug, way the hell up under the firewall, I had disconnected the wiring to the 3 and 4 injectors to make more room for my hand. Well I didn't get the number 3 plug fully connected :facepalm:

. No more lean code. It always pays to double check everything you've done when working on something and I should know this well enough by now

TobyU · Sep 13, 2019

blackburb said:
So as it turns out, when I was working on the number 4 spark plug, way the hell up under the firewall, I had disconnected the wiring to the 3 and 4 injectors to make more room for my hand. Well I didn't get the number 3 plug fully connected . No more lean code. It always pays to double check everything you've done when working on something and I should know this well enough by now

That really doesn't make sense. If an injector plug was off or intermittent it would cause a miss which should be reported as a P0303 in this case either hard code with check engine light or pending code not yet lighting light. But maybe the comp sensed the lean faster than the misfire if the engine was still really smooth.
I think they still use the pulses and rotation and crank sensor etc to sense which cyl is causing a misfire. It doesn't really know if you pull number 4 coil wire connector off it just sees low power or slower revolution or stumble that would be caused IF 4 misfired.

Bank 1 lean P0171

blackburb

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Rich_007

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TobyU

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