poor fuel economy

[99silveradodude]

i did the plugs and wires about a year ago, i will try the filter. my father is very against putting any more money into this yukon, but i will try. thanks again.

[PitchBlackC3]

on a 2003 Yukon it has the same fuel filter as the trucks....UNLESS it is Flex Fuel, then it has the quick connect fittings.

[Paulster2]

O2 sensors with alot of mileage get lazy and will give poor MPG's. But only the upstream sensors.

This is where I'd go ... doesn't sound through any of the posting these had been replaced. I'm going to be in need of doing mine soon as well.

[RedHeartbeat]

Reduce weivht as much as possible. Install a vacuum gauge and keep it as high as possible while driving..

[99silveradodude]

i will pull out the extra seats, and replace fuel filter, how many o2 sensors does the car have, and how many do i need to replace. thanks agian.

[aj06bolt12r]

The ones they are refering to for fuel mileage are the front two. So you need two of them. They can be called upstream sensors, becuase they are upstream of the cat converters. There is one for each side of the engine and they are the two that are closest to the front bumper.

To answer the rest of the question the truck has four of them. The other two do not effect the fuel trim, they are there to monitor the cat converters and tell the pcm they are there and doing their job. Have you noticed a lack of power? If not then I doubt the cats are causing your lack of mpg. If you are getting gas with more ethanol it will reduce mpgs too.