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I understand the concept of using the anti-fouler in the rear O2 sensor in hopefully turning off the MIL....but here's my question....will things function normally from a gas mileage perspective? Specifically, will the gas mileage be the same doing this trick vs. replacing the O2 sensor(s)??? If you are getting say 2 MPG less using the A-F vs replacing the O2 sensors, it would not take long for the extra mileage to pay for the sensors

Prefer an answer from someone knowledgable than guesses..no offense to anyone

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The rear just checks the performance of the Cat. If your cat is not performing well, it will only buy you time untill your nex emissions inspection. The rear O2 sensor is so cheap why not just replace it?

 

 

 

nipper

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The trick only works for the rear O2 sensor. The rear O2 only checks the efficiency of the catalyst, and has no effect on fuel mileage. The ECU compares the readings from the front O2 sensor with the rear and expects to see a certain amount of difference between the two. If that difference is too little it sets a code and illuminates the MIL.

 

If you were to use an anti fouler on the front O2 sensor there is a good change the car would not run correctly. The ECU would get an extremely lean reading from the sensor and try to enrich the A/F ratio until the sensor reads correctly. Which would actually make the mixture extremely rich.

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Front O2 is for mixture adjustment. Rear O2 tells the computer nothing useful as the catalytic conveter has destroyed any potential information that could have been gathered. It is ONLY to check that there is a percentage difference in HC's between the front and rear sensor's.

 

You could completely remove the rear O2 sensor and besides a code P0420 you would see absolutely no change whatsoever in the fuel consumption. The engine would continue to run in closed loop operation from the single front sensor.

 

GD

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so if your front o2 and cat converter are working properly, as well as the rest of the engine, the rear o2 isn't needed. they added it to make sure the cats were working, or hadn't been removed.

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Okay,,,but heres the thing...I have a P0420 but of course I dont know if the front or rear is bad right?

And the CEL is lit

So, are we saying that if the rear is shot...the anti fouler would solve the lite as well as having normal gas mileage?

 

And if it is the front that is bad...putting the anti fouler in the rear will change nothing (lite will stay on)?

 

I could dump 200+ by buying both from the west coast...but I have more in this baby than it is worth....block from CCR...valve job, brakes all around a bit of body work...the works.

I would love to avoid another expense

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this is just like everyone else faced with O2 sensor issues. based on your feelings maybe this is a good way to proceed:

 

do the anti-fouler.

 

if you still have the code, get a new sensor.

 

if you don't like the gas mileage, get a new sensor.

 

the antifouler isn't going to affect gas mileage but will protect you from unwanted CEL's.

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If you think the front O2 is bad or slow, then just get a bosch replacement - they are like $30.

 

If you still have the code invest in the $8 anti-fouler.

 

Or better yet - do them both at the same time so you don't have to worry about it.

 

It sounds like you have been WAY to nice to that car. It's an old car and it's not going to hurt to use non-OEM parts on a few things. This aint the space shuttle - don't treat it like it is. There *are* things I will only buy from the dealer but when there are good alternatives I will take them.

 

GD

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