Power loss at mid throttle

I have a 2000 tundra SR5 with a 3.4 L V6. it idles fine and runs great if the petals on the floor. it loses all power in mid range of the throttle. Having a hard time figuring out what is actually causing my problems. If any of you have any suggestions, I would greatly appreciate it

 

Is the check engine light on?

 

Also, do you have any way to actively monitor what's going on, like a code reader that supports live data?

Was any maintenance done to the vehicle in the last year or two which could be related to fuel, ignition, drivetrain?

What you describe could be any number of things, from a bad coil pack, to an a/f monitoring or TB problem, to something in the fuel system. Just in the fuel system alone, it could be that the fuel pump relay isn't kicking the fuel pump into high, the fuel pump is failing, or anything in between other than the fuel filter, because the fuel filter (when present) is never the problem.

 

TPS, MAF, TB are all suspects. Each would also be capable of triggering a CEL for malfunction. Any codes?

 

Throttle position sensor is my bet. Does the problem get worse as the engine heats up?

 

I had the 3.4 in my last 4Runner. Bought it used and it performed like a turd when I first got it -- ran fine but mid/upper throttle performance was atrocious. Cleaning the MAF sensor completely transformed it.

 

New MAF new filters. Do have codes for O2 heaters. No matter the temp you must drive it less then 1700 rpm or on the floor. If it was fuel it shouldn’t run good on the floor. It is cable driven so no TB. Not able to do live data.

 

Is there a reason you haven't replaced those with new Denso brand units already?

Because, if it's for upstream sensors, that's likely your whole problem. O2 sensors aren't just for emissions, the upstream specifically are crucial for the ECM to understand whether the air/fuel mixture it's using is valid, by checking the mixture after combustion. They're also what's preventing your cats from getting clogged up and causing even more issues.

This part is on the list of "only use OEM brands, or regret it", it is not a part where you want to use any brand other than Denso (ask this guy, he's one in a long line of victims). You also don't want to buy the parts from a well-known source of knockoffs like fleaBay or scAmazon.

If you need or want help sourcing the correct part numbers to buy, and a place to get them cheapest, please give the codes and tell us whether you're 2WD or 4WD -- you should've started your post with code info, this suggestion would've come way earlier.

 

I have to replace the cat and the sensors together due to rust and it’s not in the budget at the moment. I figured it could be part of the problem but not enough funds for it. Has 224000 on it and I think it’s all original not sure.

 

What codes do you have currently?

 

Just the heaters

 

P0135? P0141? P0037?

Just trying to figure out what you're looking at here, and maybe throw some numbers/suggestions at you.

 

Hey @fostwill7 you may want to check out this thread: https://www.tundras.com/threads/loss-of-power-under-load-solved.135081/

I know I bag on "never the fuel filter", but clearly someone already replaced the OEM fuel filter with something non-OEM. It's not fun to change, and just like with oil and air filters, I'd recommend buying OEM on that part.

Would be interesting, and a low-buck, knucklebuster, to swap it out. I don't wish that hassle on anyone, but ... Maybe a cheap fix?