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A few questions regarding P0171 -- System Lean Bank 1:

  1. If there is a problem with the fuel-air ratio, which this is basically about, why is it limited to only one of the two engine banks of a V6?

  2. Are there guidelines/heuristics to determine whether the cause of this is air intake (such as dirt around the MAF sensor or vacuum leak caused by a hose puncture) or the fuel pump is weak inadequate? Since I am also getting P0101 - MAF, I am inclined to think the former. I replaced the MAF sensor a couple of months ago so it shouldn't be that.

  3. I noticed the fuel efficiency is slightly off. Could this be the reason why?

  4. How safe is it to drive the vehicle?

Other than the CEL and 3. above, the truck (2007 Tacoma V6) is running fine.

amphibient
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1 Answers1

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  1. Its limited to bank 1 because unmetered air is only going into one side (3 cylinders). So basically air that is not being registered by the MAF is getting in after the intake manifold divides. Other possibility would be that bank 1 fuel rail/injection pressure is low, but i would think it would affect performance if that were the case. You could check it with spraying propane or starter fluid around that side and listening for a surge, although due to fire risk i prefer using water and listening for a drop in power (check out a scanner danner video).

2.you could try some MAF cleaner as well as cleaning the connector. Idk of specific hueristics that would pinpoint the exact cause. Also check your air filter.

  1. Yes, this is exactly why. System is running lean with too much air, so it tries to compensate by dumping more fuel in combustion.

  2. Safe? Yes, sort of. your fuel economy will suffer and with all that extra fuel your catalytic converter could eventually melt.

Dont Know
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