Gas Mileage

[don1555]

1993 Lumina, 3.1, 6-cylinder. Gas mileage is down to 12 miles per gallon. I was previously getting 17-18 mpg. I have replaced fuel filter and ignition coils. Any suggestions for better mileage.

[jeffcoslacker]

What kind of driving do you do? Are there any other symptoms (bad idle, stumble, miss, sooty exhaust, etc)?

That's pretty horrible mileage. Lots of causes, from engine to dragging brakes to bird nest in the airbox. Need some info.

[don1555]

Originally Posted by don1555

1993 Lumina, 3.1, 6-cylinder. Gas mileage is down to 12 miles per gallon. I was previously getting 17-18 mpg. I have replaced fuel filter and ignition coils. Any suggestions for better mileage.

The car is running rough, idles rough, sometimes it stalls when I pull in my garage or in a parking space (stalling is occassional and is only when moving very slow, as in pulling into a space or garage). It idles around 500 rpm's. The car runs fine when it get to 25 - 60 miles per hour. But gas mileage is not good. Most of my driving is on surface streets. Highway gas mileage is about the same.

[jeffcoslacker]

Just a shot in the dark, but I wonder if you aren't overfueling for some reason. Pull a plug out and see if its black and sooty.

If it is, it's throwing too much fuel, need to check fuel pressure regulator, maybe injector leak test. But if it was that rich, it should be lighting the service engine light.

Maybe change the O2 sensor(s), that'll make 'em waste fuel too....make sure the air filter is good and the intake path is unobstructed.


If you have access to a vacuum gauge, see what you read at idle. should be 18-21 hg and steady.

[richtazz]

check engine light on? any trouble codes pulled? Any recent repairs done besides coils and fuel filter? give us some more specifics.

[don1555]

Check engine light goes on and off. I have not pulled codes but when I took it to the dealer for a diagnostic they told me I needed ingition coils. Replaced the coils, still bad milage.