Suddenly bad milege on my Elantra!

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Originally Posted By: JHZR2
Winter gas?


Beat me to it. Lousy fuel.

Or maybe your ECU (for unknown reasons) has a "limp home mode" rich run mode. I would get the codes read.
 
How does this problem fit into the thread about synthetic oils and mpg increases, out of curiosity?

Originally Posted By: flinter
Is the oxygen sensor the same as MAF sensor?


No, MAF measures air volume coming into the engine, oxygen sensor measures oxygen in the exhaust stream.
 
Originally Posted By: flinter
Is the oxygen sensor the same as MAF sensor?

No.
You have two oxygen sensors.
1 you can see as you look down on the front of the engine it has a wire coming out of it. This one reads the O2 content of the burnt gasses for the computer so it can adjust the fuel mixture. The other one is in the exhaust pipe after the cat and just checks the first cats function.

The MAF sensor is in the air pipe and it reads air flow and tempature.
If you had a O2 sensor problem you would have a code and light up the check engine light.

How much of a drop in mpg's are we talking about?
 
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Does the second sensor after the Cat ever go bad or gets 'lazy' without setting off the engine light ?
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Originally Posted By: LT4 Vette
Does the second sensor after the Cat ever go bad or gets 'lazy' without setting off the engine light ?
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Yes they can. BUT it would not affect mpg's cause it is only there to check the cats and light the idiot light.
Ken
 
Originally Posted By: Ken42
Originally Posted By: flinter
Is the oxygen sensor the same as MAF sensor?

No.
You have two oxygen sensors.
1 you can see as you look down on the front of the engine it has a wire coming out of it. This one reads the O2 content of the burnt gasses for the computer so it can adjust the fuel mixture. The other one is in the exhaust pipe after the cat and just checks the first cats function.

The MAF sensor is in the air pipe and it reads air flow and tempature.
If you had a O2 sensor problem you would have a code and light up the check engine light.

How much of a drop in mpg's are we talking about?


Not necessarily.
 
2 mpg down from what? if it is down 4 or 5% then winter gas and maybe tire difference because NEW tires usually are larger in circumference by several percent. In addition; one needs to compare several full tanks of fuel usage to get any kind of average.
 
We need more information.

- When did this start?
- You said your MPG is down by 2. What was it?
- How closely do you watch your mileage? Do you log it every fill-up, or is this an "I know last summer it was higher" kind of a thing?

My mileage always goes down by at least 2mpg in the winter.
 
Its definitely old enough to run to the dealer and get a new thermostat.

And, try a couple bottles of FI cleaner form Redline, Amsoil, 3m, or Techron.

I also prefer 35-38psi tire pressure.
 
Originally Posted By: flinter
Why do you guys have to be so mean?

Im just asking a few questions.


If you really want help, why don't you answer some questions?

Like what Nate asked above, and others that are trying to help.
 
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