Alaska90

so, i'm reading the O2 sensor threads and it got me to thinking.

i have the v6, 1990, 190,000 miles on it. and, it still has the original O2 sensor. my mpg are the same as when the truck was new—15ish or a bit less in stop and go city, and 20+ for highway.

assuming at some point i do change the O2 sensor, is there anything else that needs to be adjusted at the same time? that is, if i do the sensor myself do i also need to do a tune-up? adjust idle? or?

thanks.

scope103

A tune up? As in, new points? No, the traditional tuneup from the bygone days of mechanical distributors is no longer needed.

But all the things you mentioned are things you do a) on the schedule, or if not specified, b) when you NEED to do it. Your owner's manual has the schedule, and I'll bet it says replace the O2 sensor every 80,000. You could test it, but I would just swap it out. You check the idle speed every 15,000 (is yours correct or not? The O2 sensor won't change it.) You replace the plugs every 30,000. If you have the 3vze, you replace the timing belt every 60,000.

I get the sense you've never looked at the maintenance schedule. Rather than ask strangers on the internet, I would recommend you start there. It may give a bunch of ideas for things to catch up on.

rworegon

http://www.4x4wire.com/toyota/4Runner/tech/O2_Sensor/

TNRabbit

I almost guarantee an increase in fuel economy when you change that old O2 sensor~

BMcEL

And since no one else said it...do not use Bosch O2 sensors.

TNRabbit

Also, PB Blaster the crap out of the bolts every day for a week before you try.

I also scrubbed mine with a wire brush to get all the rust off & get to the actual bolt~

Ended up cutting mine off. CAREFUL DO NOT CUT INTO THE BOLT! You'll probably have to chisel/Dremel the gasket off, too. Be sure the one you buy (Denso) has the gasket included. Might as well go ahead & get 2 new nuts, too.

Alaska90

"I get the sense you've never looked at the maintenance schedule. "

next thing your going to tell me i should change the oil more than once a decade!




i probably framed the question poorly. i'm wondering if, when the O2 sensor is changed, anything else needs to be done to account for the fact that there is a new sensor in the system. but, from reading the 4x4wire link provided above, it sounds like the computer will adjust and recognize the new O2 sensor. (i thought i remember reading someplace at sometime, that there was more to replacing the O2 sensor than just the mechanical replacement. but, maybe is dis-remember that...)

as far as not having replaced it prior, when i asked my mechanic about it he always said it tested fine and to not bother. since, so far as i'm aware, the only danger in running a bad O2 sensor is poor gas millage (haven't noticed any reduction) and not passing emissions tests (which i always passed.) i figured "if it works, don't mess with it."

thanks all for this great forum.

BMcEL

I always pull the EFI fuse for 30-60 seconds to reset the computer after replacing sensors. It will then re-learn everything instead of using it's memory as part of the calculation process. Probably not necessary, however.

If the O2 has 190k miles on it, it is way overdue to be changed. They can pass a resistance test and still be bad. I bet you'll see an increase in mileage with a new Denso/NGK unit.

rworegon

The FSM indicates a 80,000 mile replacement for the O2 sensor:
http://www.ncttora.com/fsm/1990-1995...a/maintena.pdf

http://www.ncttora.com/fsm/1990-1995...es/repair.html