Lately my car has been getting bad gas mileage. My most recent was 180 miles to the tank with premium unleaded. That is about what I have been averaging as well. My car has also been bogging big time lately too. I have also smelled a little raw gas when I start up my car. Do I need a new O2 sensor? My car has 53k miles with the mods in the sig.

 

With that low mileage, you wouldn't think that you'd need a replacement O2 sensor...but that could be it. Does your car stall occasionally? When my O2 sensor was fried, the car would run erractic under 2200 RPM, then it would work fine (because it was getting a decent amount of air)...you seem to have all the symptoms listed except for stalling. It's worth a try anyways.

About the 180 miles per tank...that's pretty good. I guess you drive conservatively? I drove a little harder in my RS...got like 150 miles per tank.

 

If I don't punch it a lot, which is most of the time now that I do I can get between 280-310 miles per tank. And my motor has 114K on it!!! That's right at 20 mpg. See if you've got any codes, but if I remember right, O2 sensors are only good for about 30-40K miles. So it's prolly your best bet.

 

Well as a matter of fact, my car DID stall while making a U Turn the other day. I thought it was a fuel problem. This only seems to happen when the car is cold, after it warms up, it is fine. I am showing no codes, should I just replace the sensor anyway?

And no, I don't drive too conservatively. I have some "spirited driving" to blow out the carbon a lot .

 

o2 sensor only is looked at when engine reaches a warm operationg temp. If it runs bad all the time it isn't the o2 sensor, it's something else like timing.

 

True, I forgot about that.... so it does sound like a fuel problem. I dunno, sometimes stuff like that is really hard to pinpoint.

 

Well it doesn't run bad all the time. Only when it is cold. That is the only time that I have this hesitation/stalling. Could it be the fuel relay?