[lanz0r]

Recently I've been getting 12.9 MPG in my 2.5rs, it's completely stock exept for the K&N Panel Filter, I get a CEL for my knock sensor, it comes and goes, could this be the problem? or maybe my o2 sensors are going?

 

[Supers587]

Any CEL will dramatically reduce your MPG's. Clear it and get it fixed and you should be fine. Other than that, check the normal stuff... tire pressure, plugs, wires, air filter, fuel filter, pcv etc etc.

 

[ride4life32]

plugs, plug wires are cheap and help alot as well o yea and a pcv valve. its cheap and very eas

 

[lanz0r]

I just changed all that exept the fuel filter lol

 

[2slo4u]

Maybe some of the oil from the k&n is fouling a sensor in the intake tract? Otherwise, that is some seriously poor mileage. Is it an auto as well?

 

[JDMGC]

my AT getting 15mph on city..lol

 

[Subru]

I have a 1.8 that's sometimes been under 15. Don't worry too much, just get the problems fixed.

 

[lanz0r]

It's 5MT

 

[2slo4u]

Are you sure you don't have a partially clogged catalytic converter? wow

 

[G_2.5rs]

sorry to hijack, but would a bad 02 sensor cause bad mpg?

 

[Jefff]

sorry to hijack, but would a bad 02 sensor cause bad mpg?

yes....

to the OP: are u knocking? do you hear pinging?

 

[Mikey B]

yes it would. would make alot of things go bad. can burn up your cat (the converter kind) and really toast your plugs

 

[lanz0r]

I'm not sure what knocking or pinging sounds like so I don't really know

 

[ride4life32]

you would know if you head it, it would sound like a sub machine gun type noise (well a pinging that fast, but more of a pop pop pop usually in the higher rpm range over 4k

 

[2.5rsleeper]

That's exactly the mileage I was getting when A/F sensor went bad. But I had a CEL for it.

 

[lanz0r]

A/F Sensor?

 

[Jefff]

A/F Sensor?

front o2 sensor

 

[lanz0r]

I'm going to replace my knock sensor today and see if I get any improvement

 

[lanz0r]

Just replaced the sensor, and drove around for about 23 miles and the gauge barely moved, I'll keep driving it a bit to see if my problem has been solved, I'll keep you guys posted.