crammit442

I posted this over on Toyota Nation and haven't gotten much response. It's been so long since I've needed any help or had questions that I couldn't remember the name of this forum. I used to just lurk here a few years back. Since it's a Toyota() I don't usually have any issues I can't fix so I haven't been here in a long time. When driving in the 50-60 mph range and midway uphill or accelerating where the trans would normally automatically downshift out of overdrive into 3rd gear, I'm getting a shudder as though the trans can't/won't make the decision whether or not to drop gears. If I go ahead and depress the pedal to accelerate manually, the trans shifts to 3rd gear w/o any problem. After doing a lot of reading, I'm wondering if it's not solenoid, throttle position, or fluid/filter related rather than mechanical. The trans doesn't make noise or do anything else abnormal. It's been doing this for a few weeks and hasn't gotten any better or worse. The transmission light finally lit up on the dash last night. Checked fluid. Clean, red, and no burnt smell. Added Lucas transmission slip fix with no real difference. Oreily's recommended Dr Transmission Shudder Fix. Small tube of red friction modifier. No big difference. Got code read and came up with PO133 : "(Bank 1) Front oxygen sensor slow response". Does that make any sense to anyone? I've read everything I can find and have found mostly mixed opinions. I've also wondered if what I originally perceived as a transmission problem is not actually an engine stumble related to the "PO133 (Bank 1) Front oxygen sensor slow response". If I understand correctly, the front O2 sensor is partially responsible for reading air/fuel mixture and plays a role in the way it's kept in the correct range. My question is could the front O2 sensor while under slightly heavier loads when the transmission is about to automatically shift up or down cause the engine to miss enough to "feel" like a transmission issue rather than a fairly major engine stumble/miss? I would REALLY rather not get into a transmission wild goose chase if that isn't actually the problem. Hopefully someone who's experienced the same issue or better understands codes and symptoms will have an educated idea on my problem. If the O2 sensor could actually be the issue, I could always grab one from the local pull a part (assuming its pretty unlikely that it also has a bad front sensor) for only a few dollars and if it fixes things, then actually buy a new quality one. Thanks very much in advance!

Charles

vital22re

iTrader: (2)

engine problems can be multiplied by the transmission. The transmissions on these rarely fail. But they are prone to the strawberry milkshake, check your radiator. If the transmission light came on it may be in the history codes. A good scanner will show history codes.

crammit442

No milkshake. Manual (Haynes) doesn't directly address this problem, but mentions throttle body cleaning and possibly trans solenoids. Where would you start with diagnosis? I can't find any vacuum leaks. Fluid and radiator are super clean (Toyota brand fluids ). I'm sure the dealer (We have a VERY GOOD DEALERSHIP), but I'd hate to spend money if it turns out to be simple. Thanks for info so far and in advance! FWIW, if I briefly turn off overdrive it shifts back to 3rd and then smoothly shifts back into O.D. When i turn O.D back on without issue.

vital22re

iTrader: (2)

Hows the coolant temp? Grab a scan tool thats capable of showing live data and see what the ECT is. If it isn't reading that its fully warm it may keep overdrive from kicking on or staying on.

crammit442

Its been a long time since I posted this, but I thought I should post what I found. I should have thought to check this first, but it turned out that one of the plug wires was on it's way out. Since each wire fires two plugs, there was a significant miss when the motor was under just the right amount of load. Replaced one plug wire and all was well! I suppose if my truck needs plug wires every 300,000 miles, I can live with it. Thanks for all the helpful suggestions.
​​​​​​​Charles

vital22re

iTrader: (2)

Great that you got it figured out.

dropzone

iTrader: (6)

Good deal..
FYI - Haynes manuals suck, generic info with some specific pics every now and than
spend sometime online and find the Toyota FSM, download it as the links have a tendency to die.

Mntbiker

had bit of trouble with mine & it was the solenoids they finely gave out. But another problem with idle led me to the amf it has a hidden air adjustment screw, which seemed to have an effect on my automatic transmission shift points.it let air bypass meter. Not really sure if it's supposed to have that effect but did on my 87 4runner