O2 sensor replacement.....

[77'911]

The mpg was getting progressively worse over time, and the rest of the fuel system has/had been dealt with. The O2 sensor was original and showing it's age(see pic). I had to use map gas torch to remove the hardware, and even then, the top of one stud snapped off(uuugh). Cleaned up the threads and bought some new stainless hardware(8mm x 1.25) which worked well. The old 1990 4runner also got a new Denso air filter installed.
Well, after the truck was running, the exhaust was noticeably "leaner" and running better. PSA to those out there, check your O2 sensors. Hope this helps others out there.
regards

 

[bills86e]

The 02 sensor should be replaced every 60k. It tells the computer how much gas is required for best fuel economy. You won't normally get a check engine light when its on its way south, only when its completely failed!

 

[4runnin83]

The 02 sensor should be replaced every 60k. It tells the computer how much gas is required for best fuel economy. You won't normally get a check engine light when its on its way south, only when its completely failed!

I agree. Even though hes a Bills fan =X

 

[77'911]

I can tell already, the truck runs 100% smoother and a bit better performance. The truck seems to reach full operating temps quicker as well. This will probably help the mpg. Interested to see what mpg looks like on the next fill up.
regards

 

[4runnin83]

Did you replace both? Or just 1? How much were they?

 

[Diverse4runner]

There should only be one.

 

[77'911]

o2 sensor replacement....

Did you replace both? Or just 1? How much were they?

Just replaced the front. I don't believe ours has a rear unit. The Denso sensor was $79 + free shipping from autohausaz.com(no affiliation). The local Toyota Dealer in WA, wanted $163 + taxes(about 9% now).
regards

 

[bills86e]

2nd gen's only have one. They do have two temperature sensors, one for the gauge and the other (recommend a new at every 60k's) is for the ECM. Both of these are key economy players.

Things changed in 1996 when OBD II arrived. Upstream & Downstream.

 

[4runnin83]

2nd gen's only have one. They do have two temperature sensors, one for the gauge and the other (recommend a new at every 60k's) is for the ECM. Both of these are key economy players.

Things changed in 1996 when OBD II arrived. Upstream & Downstream.

Ahh gotcha, thats where I was confused.

 

[Diverse4runner]

2nd gen's only have one. They do have two temperature sensors, one for the gauge and the other (recommend a new at every 60k's) is for the ECM. Both of these are key economy players.

Things changed in 1996 when OBD II arrived. Upstream & Downstream.

Both of those sensors are on the back of the motor in between the motor and the firewall on a sensor cluster.