2000 tundra power loss and shuddering when decelerating

2000 tundra 4.7 2wd. No CEL no codes. experiencing power loss from a stop and when running. pedal to the floor gets me about 50. Also experiencing a shuddering/vibration around the TC transmission area when decelerating. Noise starts when I disengage the throttle and stops when I reengage the gas. It sounds like a rumble strip or a muffled mini gun. preformed a back pressure test on both sides and everything is below 3.0 psi when at 2000 rpm. ruled out a plugged cat. did a stall speed test and got right at 2000 rpm. pretty sure its the Torque converter but I'm not sure why it would be causing that noise/ vibration, unless its something the the lock up system. Any help would be very helpful thank you!

edit: have not does any thing with the trans fluid but looks clear and red from the
dip stick. Also in neutral engine will rev well past 2000 but in drive/ stall speed test wont go past 2000

 

Just to be clear, you scanned for codes, and aren’t relying on a light to tell you, right? ‘00-04 used a halogen CEL bulb, and those burn out.

Only for shits and giggles… have you pulled the negative battery cable for 10-15 minutes to force a re-learn just to see what happens? Your symptoms suggest it may not be the issue BUT, it’s also a free test that will rule out a few things.

That said, symptoms remind me of a torque converter going down the shitter OR a bad coil. I’d confirm the plugs, check the coils, only to ensure this isn’t an ignition thing. Only because we’ve seen trucks act retarded with misfires without throwing codes. I could also see this being a leak but ….

 

it was throwing a po135 code but I replaced the o2s its running a little smoother now but still extremely reduced power and the noise is still there. What would it need to relearn or ruleout?

 

Relearn is triggered when negative batt cable is off for 10-15 min.

All of the symptoms you describe could 100% be caused by O2 sensors. Knowing these trucks are absurdly sensitive to electronics and the only proven fail-safe brand for O2 sensors is Denso, from a reputable source that isn’t fleaBay or scAmazon, the biggest source of counterfeit parts on the planet; let me ask:

What brand of sensor?
What part number(s)?
And where did you buy them from?
You didn’t need to cut wires, right?

 

I assume the truck needs to be running while the negative cable is disconnected?

I got the Denso one from orileys. PN 234-420. I did indeed need to cut wires. I see now it has three stars... they dont tell you that at the counter. something weird i noticed. I took out both o2 sensors before the cat to do the backpressure test but the one I needed to replace came out way easier than the "good" one. makes me think its a cheap one that needed to be replaced and it looks exactly like the one i bought... I didn't make this connection until I got home to swap them

 

Never, ever, ever cut O2 sensor wires. Upstream sensors tell the ECU how the engine is running. Always use the exact fit sensors. I fucking hate the big O parts store. Ugh.

Truck off. 10 minutes neg batt cable off.

Do you still have the harness? Look up the correct part number at www.densoautoparts.com

The “exact fit” sensors. For your truck, careful to pick the right ones, sometimes they’re different for 2WD/4WD

 

denso gave me the same number 234-4209. Im not sure what the harness refers to but I spliced the old connector on the the bare wires on the new o2 sensor. then I took a cutting disk to the old sensor and used the threads to make a backpressure gauge fitting.

 

let the truck sit for about 25 minuets disconnected. took it for a drive and the engine is running smoother and some of the power is definitely coming back when up to speed. still pretty sluggish when accelerating from a stop though and the vibration when decelerating is still there.

 

Never disconnect battery with engine running. That can damage diodes or ECU.

 

The vibration in question….

How many miles on this truck, and you are owner number … ????, having it for ???? miles now?

Is it from all speeds while decelerating, and/or is there a specific speed you must reach to trigger it? Like, if you decelerate from 35 does it happen, same as 65? Or only at the faster speed?

Where do you feel it, in the seat, in the steering wheel, at the pedal?

What happens if you give it some gas OR brake, does it go away, or continue?

Have you done any checks of your u-joints and/or do you know if any have been replaced at its current mileage?

Have you at least inspected the carrier (center support) bearing to ensure all mounting hardware is intact, rubber is good, no obvious signs of issues? (It’s rarely the issue, I’d suspect a u-joint more than anything here….)

Have you done any basic checks at your wheels (for bearings, steering)?

 

206000 ive had it for about 8k. yes i need to get up around 40 then slow down to really hear it. it sounds/feels like its right Infront of the center console under the floor board. i went and shook everything pretty good last night. u joints seems fine no play in the joint and seals are good. but there is a little bit of play where the yolk meets the extension housing when i move it up and down. starting to think its the extension housing bearing. I haven't checked the wheel bearing but it really doesn't sound like them.

 

now giving a po753 code

 

Well, it's sounding like that would point to transmission... And you're sure you checked the fluid level and used the proper marks for hot/cold when checking?

 

yup just went and checked it again. fluid is well above the hot mark at operating temperature. Ive never added to it though and Ive had the truck about a year

 

You may want to get the fluid level right, reset the code, and just roll to see if your issue is solved, or if some over-fill damage is already done.

Not to be cap't obvious or anything. Others have thrown solenoid codes before, some have replaced depending which it is. YMMV. I don't do well with transmissions.