The P0171 Code everyone hates.

Before I hear there are multiples and dozens of threads talking in this subject, I have looked through hundreds of the comments and yet to receive a similar experience.

2002 Tacoma 3.4 Prerunner Crew cab.

Here is where I am at.

P0171 code pops up after I pull the fuse for the ECM and reinstall.
Not immediately however. Roughly 40 miles later it comes on.

What I have noticed is, after cleaning my MAF the truck runs extremely rough with no power at first. Usually takes a 5 or so minutes of trying to accelerate before she gets back to normal and power comes back.

my process:
Clean MAF
spray starting fluid around all vacuum lines, throttle body, and intake. (No change of sound)



this lack of power leads me to believe it could do something with a lack of fuel. I may be wrong however.

fuel filter is on the way.

anyone had similar experience with this?

 

2004 extended cab 3.4 4x4. My lean code was brought on by a bad fuel pump. Cleaned MAF, etc. Sprayed to detect vac leaks, nothing. Short and long term fuel trims varied between +15 to +30%. New filter installed, no change. Finally checked fuel press at connector from tank under the hood. 23 lbs. Supposed to be 40-45 lbs. New pump fixed it real good. Ken

 

One more thing: My initial suspicion was brought about by extended cranking only when warm. Turned out that fuel pressure couldn't be maintained when engine stopped, ignition off. Built in check valve at the pump bad? Cold start seemed ok so I couldn't understand why long cranking only when warm.

 

I thought about changing the pump just in case. I will say its never taken any time starting. Seems to function as normal until I try to accelerate when it wants to backfire and lose its power. But that clears up after a few seconds of holding the accelerator, (Assuming its building up fuel pressure to regulate.)

But if I let off the accelerator to stop, once I begin to accelerate after stopping it does it again. This continues for the next few minutes and a few stop and goes. Then it clears and everything functions as normal.

Side note: While this is happening it throws zero codes.

 

Interesting. Can't say I had any drivability issues other than the longer cranking times when hot. There were occasional codes for cylinder #2 or #6 misfire but that was all. Again, all was solved with the new pump (which you probably know is fun to change ). Good luck.

 

I would get some data before throwing parts at it. What are fuel trims? Could be a bad afr sensor or dirty injectors or bad maf.

 

i had that code, found pin holes in top of gas tank, got a new tank from rock auto, kept the same fuel pump but changed the sock, code went away