Need Help - MPG getting worse quickly

[kaarona1]

Hi all - I have a 99 SLE V6 with 160k miles. I used to get 400-450 miles per tank 16-17 gallons, but now I am down to bairly 300 per tank. I have not dash lights on (except ABS), so I have eliminated an O2 sensor. If I had a spark plug not firing would it trip a CEL? Would a bad EGR valve trip a CEL? I really want my MPGs back!! Any suggestions would be greatly appreciated. It has been about 40k miles since I replaced plugs, this dramatic drop seems like somthing worse.

[pwizzle]

Try putting Seafoam into your gas tank, brake booster and crank case. Also try cleaning your MAF sensor. That's all that I can think of off the top of my head.

[ThurzNite]

You're getting 17.6mpg. That's still within spec if you're auto, and not if you're 5sp.
Dr J

[JonB]

Has the air filter ever been changed?

[solara90]

idle less, accelerate slower... it all adds up. But what about air filter, tire pressure...

[kaarona1]

It may still be within spec, but it is much worse (nearly 100 miles to a tank) that it used to be. Airfilter is only 10k miles but I will check that, tires are brand new and good pressure. I have not run any fuel injector clearer in a long time, so I will try that too, but I do not expect an extra 50+ miles per tank with the cleaner. Thanks

[kaarona1]

Cleaned MAF (never done before) and filled up the tank. I will see if it helps.

[Jabraltar]

I had the same problem and the seafoam and MAF cleaning made a massive difference

[KingKevin]

let us know if it fixed anything!

[kaarona1]

Just filled up this morning... I got 345 miles until gas light came on...that is an extra 45 miles or increase of 15% just by cleaning MAF and adding a bottle of fuel injector clearner to gas tank!!

[karennb135]

I had that problem with mine. I was getting 400 miles per tank and then it started to run on less and less each time I filled her. I had already suspected suspension or alignment problems with my car, well when we put her up on jack stands we found the front left wheel wasn't spinning like it should. We checked out the brakes and it turned out that my calipers were staying pressed. So it was taking more power just to push her. We replaced the front calipers and the problem went away. I'm back to 400-420 miles per tank.... Just a thought. All you have to do is jack it up and see how it spins. That could indicate a lot right here.

[TheMack]

im actually about to try cleaning the MAF and using fuel injectors too now because im getting exactly 286.7 miles to the tank!