95blackToy

Does anyone know a way to check if an oxygen sensor is bad? Im thinking i will take the sensor out of the exhaust and plug the hole. In theory the tuck should run drastically different or turn on the check engine light if the sensor is working properly.

95blackToy

cmon guys i need some input. 42 views, someone has to have an idea about oxygen sensors

thook

Hmmm.....well, if you disconnect the O2 sensor, your truck will never go into closed loop mode. It will always stay in open loop and run richer than it needs to......unless you run modifications that could use a richer fuel mix. You might be able to adjust the fuel a bit with the AFM, but that's up to you. I'd read on that first. Try running a search.

In theory, if the O2 sensor is malfunctioning and you disconnect it, the truck should run better. This is because, in theory, the ECU is no longer receiving faulty input from a malfunctioning sensor and will run the vehicle according to other sensor input that is theoretically functioning properly. There's two ECU programs the ECU uses to operate the EFI system; on it's base or long term fuel programming.......which remains after you turn off the key, and the short term (based on O2 sensor input)....which is erased when the key is turned off and constantly changes according to driving conditions. However, the ECU also modifies the the long term according to an "average" short term behavior.

So, what this means is by disconnecting the sensor.....permanently?.....you'll probably never pass smog, but also your fuel mileage and power will never be quite what it could be (on a stock set up), although it could be close enough to call good. Up to you.

There are instructions for actually testing the O2 in the FSM. Look on the front page of this forum and find the "sticky" that says FSM's. Go to the second post of the second page, click on the link where you'll be directed to the '93 service manual online, and begin browsing. You should be able to find testing procedures pretty easily. Hope you have a voltage meter and know how to use it. Otherwise, you could more or less rely on the difference that is made by disconnecting the sensor.

Hope this helps....

Technical goodies...
http://www.autoshop101.com/forms/h44.pdf
http://www.autoshop101.com/forms/h37.pdf

95blackToy

Thanks man.I will look at that.but I wasn't talking about unplugging it just taking it out of the exhaust pipe and leaving it all connected. Then it should detect all the oxygen in the air and noticablry adjust to that. Know what I mean?

thook

Oh!!! Not a good idea, bro. You might as well just disconnect it. I'd suggest reading the link on O2 sensors I posted.

95blackToy

Alright thanks man.I'm gonna go check it out . I'm thinking that might be my problem because I'm getting 11 MPGs.and low power at times.sound like an appropriate assumption. can i use a 95 4runner fsm since its the same year and motor? I ried disconnecting it like you said but then it wouldn't even start.

thook

Same motor, same manual.

Odd. Don't know why it wouldn't start by disconnecting the O2. The O2 sensor has nothing to do with the vehicle being able to start. You've got something else going on. Which raises the question, are you getting a check engine light?

95blackToy

no check engine light. i had one before i did the head gaskets but after that it has been off.il try it one more time during the next brake in rain