99, 4Runner P0171 code

[Jheera_blade]

Hi all, I got this code (P0171) recently and am trying to isolate the problem. The acceleration is quite poor right now.

This far, I have tried the following, but the code keeps reappearing:
- cleaned the MAF censors
- replaced the fuel filter
- tested the pressure from the fuel pump, it is normal

I also pinched/blocked the return pipe from the fuel regulator and test drove the truck and it seems to be running fine with return pipe blocked. Right now I am open to suggestions about what it could be.

Also, if there is a diagram of fuel/vacuum system that I anyone has access to, it would really help if I can see it (from Toyota manuals or otherwise).

 

[toyoboy]

make sure you have no vacuum leaks. Ive also had maf sensors that needed to be replaced. cleaning just didnt do the job. 90% of the 4runners that come in the shop for that code were maf related. good luck.