'87 4 Runner 22REC 4x4. Single wire 02 sensor. New sensor, only idle time. After warm up when the rpm's go over 2500 rpm it runs rough and engine shakes. When I unplug the sensor it runs very smooth. I checked the volts at the female end of the plug with engine running, it's 51.8 m V. Is this right what else should I check? Timing has been checked and is good.

 

As soon as you pull the sensor, the ECU puts the engine into closed loop to protect its self. It basically puts more fuel in and retards the timing to predetermined maps. Your going to have to go through the entire EFI system to get at what is truly wrong.

I beleive the FSM has procedures to check each circuit:

AFM
Tempature sensor (the one that tells the computer, not the gage).
TPS
Knock Sensor
etc.

Sorry there is not a magic bullet to say what is wrong, but if I had to wager a guess it sounds like an air or fuel problem.

Let us know...

 

Do u know what the voltage should be at the plug (female) end?

 

Is there a way to test the 02 sensor itself?

 

http://www.ncttora.com/fsm/

 

See if this helps you out.

O2 sensor
O2 sensor should read oscillating voltage from .1(lean) to .9(rich)
Warm engine race at 2500 rpm check for voltage swing.
Pull vacuum line see if voltage leans out.
Introduce propane see if signal goes rich.
If no voltage swings try a temp wire from ECU to O2 sensor

Later