I noticed my gas mileage going down considerably in the past month or two. I am going to remove the front 02 sensor and see what it looks like and check my plugs just for the hell of it. Car only has 20k on it. But my main concern is the sensor. By hooking up a scanner I know I can read the voltage of the sensor. Does any one know what is a "normal reading" on it? or at least a normal range?

 

If the sensor was fouling I would think you would easily throw a CEL.

 

thats true. I just noticed that my mileage went from consisten 220-240 to around 170-200 out of a tank of gas. always the same pump at the same station. so i am trouble shooting this, and that 02 sensor is my first guess

 

CE light will pop if your o2 sensor goes bad

 

Have you been in the boost more, or driving differently? i.e. more city, light to light driving?

 

Do a pressurized boost leak test, comression test and lopok at the plugs - email me a photo of the plugs

Usually the 02 sesnor will toss a cel when it goes bad

You can verify its accuracy against a good wideband 02 sensor

 

nah, my driving has been the same. this past tank of gas I deliberately stayed of the boost and actualy drove mostly on the highway. Still managed to only get 198 miles out of 12.8 gallons of fuel Thanks for the info Al. I am going to take a look at the plugs tomorrow. I will send a pic of them as soon as I get a chance tomorrow. thanks

 

here are what my plugs look like. the order that you see them is the order that they came out of the car left to right. 20k on the car. tuned last december. so about 10-12k since the tune. thanks guys

 

subscribed...

 

well I think I found the problem. i noticed that the left side of my valve cover above the manifold was a little dirty. took the heat shield off o find my 02 housing secured with only 1 bolt! the little bastards must of rattled off somehow.. Aside from that i tried to do a boost leak test today. I started to pressurize the system from the turbo. the first 10psi filled quickly the second 10 slowly but wouldnt hold. I could hear air but not feel it anywhere. it did not hold...anyhow, I will be going to the hardware store tomorrow to get the last bolt i need to retighten it. hopefully this solves my gas mileage issue. boost leak test TBC...