to preface let me tell you I have an 03 camry 2.4L engine
as of recently my cars short term fuel trims at idle has been -20 (a new one for me) and when I accelerate it goes all the way up to 25+ indicating the engine is running lean.
Things I have tried.
Changed my PCV valve.
Clean my MAF.
Changed from Oxygen sensor to bank 1 (quality denso part)
secure my air box and change filter.
Had a new flex pipe welded on (Diy repairs kept leaking)
Used a pump transfer tool to detect any leaks coming from my Air intake. nothing.
Reset ECM
This is just very bizarre to me, I wish I can simply plug in a computer and tells me what component is causing this because I feel like pulling what hair I have left out.,

Ok, let car warm up and plug in my scan tool. examine any live stream data. Oh, everything seems very good at idle.
It's just when I accelerate my car it goes all the way up to 30 percent positive on short term fuel trims including long term.
As I drive at a constant speed say 60mph my trims go back to normal numbers.
Please excuse my grammar and punctuation for it's been a long dirty day.

Previously idle was around -3 percent short term now it's all the way down at -20. Could this simply be the MAF sensor malfunctioning because the readings are all over the place at any given day.
Tomorrow I am going to check for any vacuum leaks however, I have a hard time trying to find an 02 - 06 diagram of any vacuum line.

 

See private message.

 

Seen the message in regards to injector timing. Shouldn't the ECM handle all of this? Also I only read timing the injection to the fuel injectors is only used on modern diesels and classic cars.
Edit: sorry I misread this. You suspect a timing chain is at fault here? that seems like a steep diagnoses before checking any other issues.

 

Not timing chain. The Toyota diagnostic tool can vary injection timing to determine how this effects fuel trim in case it is an injector problem.

 

Major Update. I finally was able to fix the issue. Apparently I've been cleaning the Mass Air Flow sensor as everyone on youtube recommended.
They would like to preface to never spray up into the component because it could damage it.
I watched a german guy on youtube spray directly into the upper ports where two wires are attached and figured I follow suit.
Well, lo and behold. My short term fuel trims are back to normal. Why anyone would recommend spraying directly only on the bottom sensor with unfounded claims is beyond me.
I figured I'd order a new oem sensor while I'm at it since it's listed for a merely 60 bucks on amazon and to follow suit and clean out the injectors and redo the O rings with new basket filters.
That's a lot off my mind. now I don't have to worry about taking apart the fuel pump and filter and finding the right oem part for cheap.

 

Great job in finding the issue.

Just what did you spray?

 

Hello Friend. Sorry for the late reply, my internet went out last night and I don't wanna be the first time poster and just abandon the forums.
I used CRC mass air flow sensor cleaner.
I always see other brands however CRC has never done me wrong.
I usually stick by that brand. Anywho my new MAF just got here so I'm gonna disconnect the battery and install the new one to reset the ECM.