Well, the TPS (off the truck) read fine. Upon reinstalling the throttle body, I tested the TPS through the ECU side of the harness again and it all checked out. I took the truck out for a drive and it acted the same as normal. All TPS type symptoms. I cleared the code by removing the ECU plugs (when I was testing the TPS from that end) and got no codes from the drive. I drove the truck for about 20 minutes and got it to really act up here and there just in hopes that a code would come back and point me in the right direction. Everything checks out fine; TPS is within spec, no short or open in the harness between the ECU & TPS, all I can think to do now is replace the ECU itself. It would just be an expensive "maybe".

 

I haven’t looked at my ECU board, but apparently you can remove it and open it up to inspect the circuit card for fried components or corrosion. You might do that before you buy a new one.

 

I’ve looked given it a look already. Unfortunately I didn’t find any corrosion, debris or rust on the board or any contact points. That was about a month ago, wouldn’t be a bad idea to open it back up again sense it’s easy just to double check.

 

I hesitated to mention this because I didn’t think it was your issue, but I had a sienna that ran great for about 25 minutes and would then go into severe fuel starvation intermittently. The fuel pump passed all of the usual checks, but it was the problem anyway. It’s another expensive part, but if it hasn’t been replaced in 200,000 miles, it might be worth doing just for maintenance.

 

Cut the silicone sealant out from around the air box MAF to reveal the inner workings. Remove the cover from the air box. Spray the whole interior with 'electronic circuit/contact cleaner' not carb cleaner. Then spray the cleaner on a Q-tip and gently rub clean the flat copper arced rheostat. Reach to the under side and depress the flapper to move the swing arm to the left side like it's sucking in air. Noe make sure you really clean that right side end as that is idle and low speed position. Lastly, take a small strip of white printer paper (has some minute roughness) about 3"L x 0.5" wide to soak with cleaner. Gently slip it under the swing arm end to rest under the small contact there. Now just slide it back and forth enought to clean the contact tip.

When done, you can silicone the top perimeter and replace the plastic top. I decide to use that aluminized air duct tape to seal around the top perimeter. it sticks very well to the metal housing and removes easeir than silicone if need access again.

Mine was oxidized and sticky at the idle end so the swing arm contact would stick idle and not drop down to proper idle speed. Works like new now.

 

After some time off to focus on other things I’m attacking this again. I’ll try the MAF like you said here!

I just replaced the aftermarket TPS from O’Reillys with an OEM TPS from 22re Performance and it still didn’t do anything. It idles perfectly and GREAT upon start up. 3-5 minutes into idling it drops on its face and idles at 400rpm. If I give it a sudden burst of throttle it’ll backfire through the intake and die. It doesn’t immediately, it only will if I hold it for a split second and don’t back off. So it’s running lean. I haven’t driven it to get it to throw a code again but I will after I’m done detailing the interior.

 

It might be worth noting that when it idles rough, disconnecting the TPS doesn’t make it run or idle better nor worse.

 

Well, boys, the truck runs.
I knew that the fix would end up being something so dumb... and by the way, im late to updating this post fix. It's been fixed for a couple weeks now... The TPS adjustment calls for a 1/4 turn of the throttle stop screw after it barely touches the throttle linkage. THEN you set the TPS. I did that.... a million times. I was talking with my Grandpa after breaking down and buying a factory TPS from 22reperformance.com (which probably helped big time in this fix) and he told me to try another 1/4 turn... so a 1/2 turn total. After installing the new TPS the way I had before, it ran better but not perfect. After throwing it on after adjusting the stop screw a full 1/2 instead of 1/4, it ran perfect and has ever sense. Im frustrated but I can't be mad. The truck runs great and I'm finally able to drive it around. Now its on to other little things lol.

Thank you to everyone that helped, I appreciate it more than you guys know!

 

Good to hear you solved it. Congrats.