1992 Saturn sl1 slowly loosing fuel economy
 

I have a 1992 Saturn sl1 and over the last 8 months my fuel economy has gone from 40+ to upper 20s. I also have not lost a considerable amount of power, if I did not record my fuel mileage I would not know that there was an issue. I have did a vacuum test on to check the catalytic converter, tested the oxygen sensor, checked air filter, and pulled the spark plugs. Nothing points to a clear answer. If I cannot figure this out soon I will have to start driving my truck that gets 18mpg to save gas money!

when is the last time you changed the fuel filter?

Tire pressures? Spark plugs/wires/cap/rotor? Brakes dragging? Alignment way out of whack?

-soD

If you have a mechanical ignition like I do put a timing light in it. After I noticed a big loss in get up and go I put the timing light on my car and found the base timing was stuck at 30 degrees. That means the mechanical advance were stuck. I got really bad fuel milage for that tank too.

Go for a drive; don't use the brakes, roll to a stop. Feel the brakes for heat. That hot one that you just burned your finger tip on is dragging. That lovely Minnesota road salt has a way of doing that to brakes. And everything under there. :mad:

The car does have 230k on it, and burns oil (as Saturns do), so the first thing I checked was the cat, and the O2 sensor.

I have lost 35% of my fuel efficiency!

I normally check the tire pressures, it does not have mechanical timing, the plugs and wires are less than a year old, and like I said I pulled the plugs and inspected them. The alignment is not perfect, but the problem is slowly getting worse I don't think the alignment could slowly get worse. Could it be? I have also checked my hub and tire temps after a few long and short trips, I had a brake hose lock up a caliper in the past. I do not think it is a drag problem, as I take the same route everyday and my EOC distance has not changed. It is also not seasonal/climate thing, as I have had the car for 3 years taking the same route.

Fuel filter is the one thing I have not done.
Could a bad fuel filter cut my mileage almost in half? I just about got one before making my post, but did not think it could make that big of a difference. I am not one to throw money at a problem and hope it goes away. Maybe the car is just on its last leg...

On the end of the fuel rail is a pressure fitting.
What pressure do you get ?

I don't have a fuel pressure guage, but I just replaced the fuel filter tonight. I cut the old one open and it is covered in black sludge. So if all else I added some life to my fuel pump, I will see how my next tank goes. Hopefully that was the problem, otherwise I am out of ideas...

http://highjumphero.webs.com/photos/P5240064.JPG

Not the greatest picture, but the original orange/tan filter is covered in black sludge, easily that comes off with a wipe of my finger.

Did you check the Engine Coolant Temp Sensor? There are two on your car, one for the gauge, one for the ECU. These are notorious for causing all sorts of wonky issues when they fail.

Hey you know what, my in laws had one of those go out on their Saturn, I will look into that next...