I've heard some poeple in here suggest that you can have a bad O2 sensor on the 3vze equipped trucks, and it might not throw a code. But could it be the source of a slightly rough idle as well i.e. have you replaced your O2 sensor and it improved your idle and you noticed it helped your gas mileage? Also, isn't there some way to check your O2 senor like measure it's conductivity or something like that?

 

Yeah, you can check it with with an ohm/volt meter against the specs in the online FSM.

Interesting, I've never heard of a bad O2 sensor not thowing a code. If it's bad, the ECU should pick it up. However, just because the ECU may be throwing an O2 code doesn't mean it is bad. Just that the sensor is detecting something is wrong in the exhaust mix.

A bad O2 sensor can be the source of a rough idle, but like I already said something else may be the real source. I've replace them before and it did improve how the vehicle ran initially (idle, mileage, power, etc.), but the problem soon reappeared because something else was bad....like the engine coolant sensor or leaky cold start injector.

 

im having one shipped to me right now. im hopping that it helps my idle and my gas millage. i really need the help in the MPG department. i tested it and it was on the very edge of the specs. so i got one anyway. its nice to know when something was new and when you put it on. not just hoping that the owner before you did.

 

how many o2 sensors does the 3v-ze have?
where are they located?
pics?

 

It depends on the model and year. That I know, but I don't know the specifics. As far as location, they will be on the exhaust underneath the vehicle midstream........one before the cat and, if you have two, one after. Might wanna crawl underneath and look.

 

for my 1995 4Runner SR5

do i have an o2 sensor somewhere near the engine?

the only o2 sensor i can find on my vehicle is the one near the cat. it's right BEFORE the cat.

i ordered 2 sensors, both denso, one for the "front" and "rear"

can someone tell me where the "upstream" o2 sensor is?
and the best way to access it

 

couldn't see anything other than the one near the cat,
so i am assuming there is no o2 sensor near the engine
meaning my truck only has one

thanks

 

You should only have one IIRC.

Fink

 

The only trucks that have two O2 sensors are the California trucks, which have one before and one after the cat. All others should have only one.

 

Correct; this is so the ECU can test whether the Catalytic Converter is working (as the upstream sensor switches back and forth, the downstream sensor should be doing nothing, because the Converter reacted all the oxygen).

 

On Cali vehicles I believe the front sensor is an A/F sensor too, that's what my '99 had anyway.

Fink

 

i cant seem to find a part number for the upstream o2. can anyone help me?

 

This thread is pretty old.

www.densoproducts.com

 

I replaced my coolant temp sensor and soon to be o2 sensor. That and new exhaust maybe it'll actually pass emissions...