Drove 4runner home 2 years ago 80 miles no problem. It has been sitting in my yard. I started it up and drove it briefly, but once the engine warms up it only revs and does not go forward or reverse. The transmission fluid level is okay and looks okay. Is the train fried, or is this related to bad O2 sensors or clogged cats? Any help appreciated. I did unhook the O2 sensors and it doesn't seem to help. If I start the car up again after sitting the transmission works until the engine is Warm. Thanks!

 

Tranny troubles like this sure don't have anything to to with cats or o2 sensors.
When a worn tranny gets to operating temp, the viscosity of the fluid is at a minimum, while tranny clearances are at their max.
This makes for low internal hydraulic pressures, and consequent failure to move.
You don't say how many miles are on it, but it's likely that the tranny is toast.

 

That makes sense. The train only has 168k on it. Did have a similar problem on another 3rd generation. I unhooked the O2 sensors and it solved the problem until I replaced the cats/O2 sensors. this time though unhooking the sensors isn't working.

 

Whatever you say, but it's likely that what you did with the 02 sensors was only coincedental to your trannys return to functionality.

 

How long has it been sitting before starting up? Any engine lights? Prior trans problems?
Depending on how long, maybe a change in atf might help. I would wonder if old fluid and moisture have an effect. Kinda young for a trans to go out unless there's more to the story.

 

I decided to park the truck out. The transmission was working fine the last time I ran it even when it was warm when I pull the motor the transmission fluid was very dark brown so I'm guessing that there was two floor for a fluid change thanks for everyone's input.