P0171 Confirmation

My 2002 2.7l pre-runner has had a p0171 for maybe almost 4-5 months. Recently got a scanner that looks at live data. Code is thrown at idle looking at the freeze frame data. Already cleaned MAF sensor and no change. Don't think it's the air-fuel ratio sensor cause that was replaced 2 years ago. When looking at the live data the SFT and LFT numbers go back to normal when the throttle is open. So my suspicion is a vacuum leak since fuel trims only get worse when at idle. Just need confirmation if this sounds logical.

Also, my RPM goes down to the high 560s sometimes when at idle and the engine vibrates. Is this also a symptom from p0171? Thanks.

 

You can use a propane or butane torch un-ignited to find vacuum leaks. The gas will cause a blip in the idle and will help you find it if it is the case.

MAF's are my first suspect with that era of Toyota and P0171. Not dirty, but has failed. I would see if you can find someone to swap with to test out. Or find one at a junkyard.

 

Thanks for your suggestion. Gonna smoke the engine sometime this week. Replaced the MAF already and the code still persists.