I cant figure it out

[Tommy]

I need help my 93 festy is getting 25 mpg on the highway i have changed oil and filter spark plugs wires rotor and distributor cap check all my tires and I just dont know

[JPT]

Automatic or 5 speed?

[perucho]

That's bad mileage for a Festiva! How's that air filter?

[Pu241]

OK, after looking at all of Tommy's previous posts, it appears he has an ATX.
So depending upon how fast he drives I can see 25 MPG as not being out of line if your running 70 MPH.

Tommy, drop 5 MPH off your normal speed and see how your MPG is affected.

[Charlie1717]

How's your: Air Filter, Thermostat?, Tire pressure?.
This^ plus driving habits and it being an atx could be why your getting 25 MPG

[wybnrml]

How are you calculating your mileage? Are you using your odometer, it could be wrong. Do you have larger tires, that could through off your odometer.

[FestYboy]

have you thought of replacing the o2 sensor with a denso unit?

[TominMO]

Parking brake on? Or the brake sticking on one side?

[Charlie1717]

Parking brake on? Or the brake sticking on one side?

^^ I had this issue on my blue festy and it was virtually undetectable (No noise and wasn't even a huge difference on accel/decel after I fixed it but my mpg's went up pretty drastically.

[Tommy]

The air filter is new the tires are aired to 29psi like the sticker says it is an automatic and I drive between 55-65, I drove a month at 55 and it made no difference. What is an indication that the O2 censor is bad? And I checked the brakes they are not dragging.

[Pu241]

29 Psi is for ride comfort!

For better mileage are you willing to sacrifice some of that?

Check the side wall of your tires and find the maximum pressure they were designed to hold.
Assuming they are all the same, raise them all to 2 psi below that pressure.
This also assumes your tires are in good shape and not worn, dry rotted, or otherwise unfit to be on the road.

Then try your 55 MPH experiment again, as you already have data on it.
Then again, if it was warm at the time, verse the temps you have now, it not going to matter.
But you should see an improvement over what you got on your last tank, if you drive the same way.

[SuperDaveGulvak]

Well my 91 gets about 26 & its an auto. I drive it like an elderly person as far as accelerating goes but I am guilty of 70mph when on highway. Plugs, air filter, cap ect. look ok first things I checked. Now from what I've read on here my temp needle never gets much further than the white line at start of cold on temp gauge & that has me wondering about a bad thermostat/stuck in open loop. Could someone explain the open loop a little more & if it's possible to have in a FI or is that just a carb problem for bad mileage? Not trying to jack your thread man just figured I'd chime in w/ my auto mileage woes to see if we could get an answer since it sounds alot like my car/what I checked.

[FestYboy]

constant 70mph in my auto netted me 34mpg this past Madness... you should see 30+ easily at highway speed from an ATX

[Tommy]

I will try the tire pressure, they are new tires so they should handle it. Its okay that you ask about your car on this thread if you get solutions maybe it will help with mine. When I first started driving this car a year and a half ago it got 36mpg I rebuilt the motor and everything stayed the same I then parted it for a while so I could do body work and paint then started driving it again it still had the same mileage then just started getting bad mileage one week I noticed I had to fill up on Wednesday were before I had to on Friday before my drive home and had to fill up again on Friday when I got home. With the mileage Im getting I could drive my truck that gets 21mpg. I also noticed my lifter tapping maybe internal damage giving me bad mileage?

[FestYboy]

a tapping lifter is a collapsed lifter and seeing that your MPGs have dropped dramaticaly, i would think it's an intake lifter. that being said, if it IS an intake lifter that's failed, then that valve is opening later, being pushed open less, and closing sooner. that means one cylinder isn't making as much pressure as the others. (a bad echaust lifter can produce the same results but to a lesser extent).

i recomend a cylinder pressure check.