OK, What could be my prob, I changed the Oil, Plugs, Filters, (Gas and Air), and I have the proper air pressure in the tires! why has my trucks MPG gone from 16 to 10 in less than a month? I have a 1998 5.4l xlt! Please tell me what to do next!

Thanks

bigNAnative

 

I could be way off here, But if you are not setting codes ( no check engine light) maybe you are staying in open loop. Might not be getting warm enough to get the computer involved with mixture, timing, ETC. Do you have a short drive between stops? I am sure it must be pretty cold where you are this time of year. It's only a guess but you seem to have tried all of the usual methods. An o2 sensor or coolant temp sensor will mess thing up but would normally trigger the cel. Are you running the stock air filter? I have heard of some of the after market filters freezing up and restricting air flow. Good Luck!!

 

most likely the coolant temp sensor!

 

HMMMM, I think it might be the freezing air Filter! I do have a K&N Air filter and the past month has had below 0 temps. i think i might get a regular one until the cold weather passes! then put the K&N Back in when it warms up! if that doesn't work then i am taking it in to get it hooked up to the computer! thanks for the suggestion!

bigNAnative!

 

In some areas, low energy content winter fuel can also drop mileage, but a 6 mpg loss is extreme!

The frozen air filter certainly sounds like a possibility.

Cold winter air is much more dense (extra oxygen), and the computer should be adding more fuel to keep the air/fuel ratios correct, which could be part of the problem.

FWIW, my buddy had the mileage decline on his Expedition last summer. He had driven a bunch of dusty roads, and the wire in the MAF had gotten dusty. Apparently, this makes the engine think a lot more air is passing through and the computer adds more fuel. I believe he cleaned the MAF wire very carefully with a q-tip.

 

Have you checked your neighbor for 'gasoline breath'?

 

HMMMMM! i might have to check my neighbor! I have another question! OK I have heard that with K&N air filters, if you over oil them the extra oil tends to get sucked downt he air tub and then covers the MAF and it doesn't work right! could that be a problem to!

just a thought!

bigNAnative

 

Originally posted by bigNAnative
... K&N air filters, if you over oil them the extra oil tends to get sucked downt he air tub and then covers the MAF and it doesn't work right!

Yep, pretty much. That probably will not cause such a drastic drop in gas mileage though, mostly just rough idle. Just clean your MAF to correct the issue.

Good luck with your investigation.

 

I've got an '01 4x4 with the 5.4l. My mileage is usually around 15. Its dropped to like 11 during the winter. I've got the air force one kit. Im thinking of pulling it out and putting the stock intake back in for the remainder of the winter.

 

I have never owned a vehicle that's gas mileage is as heavily impacted by cold weather as my 5.4l Screw. A cold, rainy day can have a 3 mpg impact on my already crappy mileage. The truck runs best on clear days above 60 degrees but below 90. I think I know why people refer to their trucks as females!

 

If you decide to clean your MAF sensor,"DO NOT USE A Q-TIP"!!This will only leave small strands on the thin hair-like wires and/or break them!Use a product called CRC Contact Cleaner or brake cleaner.Either one will do an excellent job.Good luck!

 

I decided to clean my MAF today, but where is it?

 

Ok, I think I'm getting better at this. I did a search and will try and post the picture.



Looks like I take out the air cleaner and it will be there. So then it is those very small black wires that you can hardly see. I spray them with break cleaner. I'll give it a try, and take a drive.

I't snowing, so I want to go outside and play for a while.

 

I wouldn't use brake cleaner. Use a electronics contact cleaner ( available at auto parts store) It will leave no residue. Good luck

 

Well if you dont have electronics cleaner use what you got.

BrakeKleen or starter fluid are alcohol based and will do the job.