Getting bad mpg and was thinking maybe my o2 sensor was the problem (tried a bunch of other stuff, fuel filter, air filter, etc.). Only thing is im not throwing any codes. Could the o2 sensor still be beat but it isnt throwing a code? Is there any way to check it manually? Any input helps.

 

Could be a lot of different things, and usually you would get a code with a O2 such as (Lean Bank/O2 code). Could also be a dirty MAF but we need more. How many miles (didn't see sig), and have you noticed any strange sounds, vibrations, clicks? Have you upgraded anything on the drivetrain or done anything to it such as bigger tires, programmer, gears, or rims? The more you put out the better the answer you will get. Otherwise everyone on here is just throwing their best guess at you and it still leaves you to do most of the work.

 

if the 121k mileage is correct in your sig then I would replace the upstream sensors with OEM motorcrafts. I just did mine and they were less than $50 a piece from Team Ford parts.

Kev

 

Just changes my o2 upstream sensors and I also have bad mpg testing out mpg right know ill let you know

 

Upstream O2 Sensores are never a bad idea. The O2 sensors and the MAF are the main sensors that tell the ECM how much fuel to send into the engine. Over time the sensors wear out and become lazy, possibly allowing the engine to run richer than need be.

 

Thanks for all the input. And not much has been done to the truck mod wise. Yes 121000 miles and other then just a drop in k&n air filter and a flowmaster no mods to the truck. No sounds or anything weird other then once in a while as soon as for some reason when I hit exactly 38 mph there is a high pitched squealing for just a second. Can't tell from where.

 

And again, no codes. If the upstream sensors were bad sous it throw a code? Or would it maybe not?