P0171 and Poor accelerations Missing

[jcush87]

P0171, Poor acceleration, Missing

Hello, I have a 1999 v6 with error code p0171 which says bank 1 is lean. I ha e tried cleaning g the MAF already. Performance is getting worse as time goes on. If I floor the gas, the truck stumbles for a second then slowly accelerates and there are a few stum les\missfires during acceleration. If I only slightly depress the pedal, I don't have the miss and the car seems to accelerate better. Also above 3000 rpm, the engine seems to stop missing and accelerates harder until it shifts. Any ideas of what to do? I also have a 96 4runner, so I maybe able to swap parts before buying expensive sensors etc. Thanks!

 

[TheDurk]

Swap out the MAF to start. Sometimes cleaning doesn't work and only a new one will do. (Are you sure you did it right?--some people clean the wrong wire or damage the sensor or use the wrong gook, like brake cleaner.) Do detailed vacuum leak check, both hoses and boot all the way to the MAF. Swap front O2/AF sensor. Check exhaust leak before first O2. Check PCV.

 

[19963.4lsr5]

Could be also low fuel pressure

 

[jcush87]

OK, so I cleaned the MAF again, thistime more thoroughly, and the performance issues have gone away for the most part. still a slight rpm drop the instant i floor the gas pedal and the check engine light came back on.

Thanks for the help!

 

[A.Wilson013]

OK, so I cleaned the MAF again, thistime more thoroughly, and the performance issues have gone away for the most part. still a slight rpm drop the instant i floor the gas pedal and the check engine light came back on.

Thanks for the help!

I'd disconnect a vacuum line (I like the ones near the brake booster), light up a cigar, and blow some smoke into the line... Look for smoke coming from the engine bay. Theoretically, with no vacuum leaks, it should come out the air box for the intake I believe.

 

[jpshoe]

There is a ground wire that controls the MAF and both O2 sensors located near the intake plenum on the driver side. Make sure that it tight and making good contact as well. I had the same issue and it took me a few months to diagnose it as well as taking it to two shops and spending a ton just to find a loose ground wire on my own later on. Good luck!