1993 Other Saturn Models 15 mpg. HELP!

  • 1993 SATURN
  • 4 CYL
  • FWD
  • 172,000 MILES
Hi, my name is Daniel Scott. Last year I received a manual '93 Saturn SL2 (OBD1) from a friend with something like 14 miles per gallon. Before he gave it to me, he replaced the tensioner but in order to do that, he had to drop one side of the engine and afterwards was unable to start it. So he gave it to me and I got it running. When I found out about the gas mileage, I took it into a shop and had them run a diagnostic on it. Afterwards, they said everything was fine and that everything was running within specs. But I still had 14 mpg so, I continued to try to diagnose and fix the problem myself. After working on it for months, and hundreds of dollars later, I have only been able to raise the mpg to 17. However, that didn't last and now I am back down to 15 mpg. Also, when I step on the gas to accelerate quicker, it will periodically hesitate, buck a little, and lose allot of power, usually around 3000-3500 rpm just before I shift. The only codes it ever throws at me are an occasional "lean misfire" (code 44). I have researched like crazy all over the net trying to find a solution but still nothing. Here is a list of the things I have replaced or tried. Any help with solving this problem would be soooooo appreciated:

egr valve, fuel pressure regulator, air intake temp sensor, both engine temp sensors, ran 3 bottles of chevron injector cleaner through injectors and visually inspected them, o2 sensor, pcv valve, air filter, fuel filter, spark plugs/wires, and ran Sea Foam through air intake and egr lines…still nothing.
Thank you for any and all help!
Do you
have the same problem?
Monday, July 21st, 2008 AT 8:27 PM

2 Replies

Test the fuel pressure and the throttle positioning sensor. Reduced fuel economy can a be a result-see below

Most Common Fuel Wasters:

Loose or missing gas caps. 17 percent of U.S. Vehicles have a loose or missing gas cap. This allows an estimated 147,000,000 gallons of gas per year to evaporate into thin air.

Underinflated tires

Faulty thermostats

Worn spark plugs

Malfunctioning engine controls

Poor wheel alignment
Fuel Saving Tip #1: Low Tires Waste Gas
Underinflated tires and incorrect wheel alignment can lead to conditions which increase rolling resistance. This is like driving with the parking brake not fully released, it can cost a mile or two per gallon on a car that normally delivers 20 miles per gallon. Correct tire inflation pressure is critical for good fuel economy, safety, maximum tire life and proper vehicle handling performance.

Fuel Saving Tip #2:Keep your car in tune:
Keeping up with regular vehicle maintenance can improve gas mileage by an average of 4.1 percent. Results may vary depending on the kind of repair and how well it is performed. Ignition misfires are one of the biggest fuel waters of all!

Fuel Saving Tip #3: Keep Your Air Filter Clean
An air filter clogged with dirt, dust and bugs chokes off the air and creates what is called a "rich" mixture - too much gas being burned for the amount of air, which both wastes gas and causes the engine to lose power. Replacing a clogged air filter can improve gas mileage by as much as 10 percent.

Fuel Saving Tip #4: Change Your Spark Plugs
A vehicle can have either four, six or eight spark plugs, which fire as many as 3 million times every l, 000 miles, resulting in a lot of heat, electrical and chemical erosion. A dirty spark plug causes misfiring and that wastes fuel. They need to be replaced regularly.

Fuel Saving Tip #5: Improve Your Driving Habits to Improve Fuel Efficiency:

Avoid quick or 'jackrabbit" starts and stops.

Aggressive driving wastes gas. It can lower your gas mileage by 33 percent on the highway and 5 percent in the city.

Observe the speed limit. Gas mileage decreases rapidly above 60 miles per hour.

Avoid excessive idling. Idling gets 0 miles per gallon. Turn your engine off if you are going to be stopped in traffic for 15 seconds or longer.

Use cruise control because it helps you maintain a constant speed limit.

Use overdrive gears because the engine speed goes down saving gas and reducing engine wear.

Avoid carrying unneeded heavy items in your trunk. An extra 100 pounds in the trunk reduces a typical car's fuel economy by 1-2 percent.

Use air vents to circulate air instead of air conditioning.

Fuel Saving Tip #6: Practice Preventive Maintenance:
Simple preventative maintenance steps that you can do to conserve energy, protect your investment, improve highway safety and benefit the environment include:

Regularly changing your motor oil. Dirty oil can reduce fuel economy up to 1 mile per gallon! To maximize fuel economy, use a 5W-20 or 5W-30 synthetic motor oil.

Keeping your tires properly inflated (32 to 34 psi is about right for most cars)

Taking your vehicle for annual brake inspections (Dragging brakes can waster fuel).

Get your transmission fixed. A slipping automatic transmission can cost you 1 mile per gallon or more. It's the same story if you have a manual transmission with a slipping clutch.

A bad cooling system thermostat that causes your engine to run too cold can reduce fuel economy up to two miles per gallon
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Monday, July 21st, 2008 AT 8:38 PM
Hey thank you for the suggestion about the throttle position sensor. I did test it and it was out of range in both idle (high) and full throttle (low). So I replaced it and it did improve its gas mileage and overall performance, but I still have like 18 mpg city+highway.
As for your suggestion that I test the fuel pressure, I tried but the gauge my dad has is really old and hard to read. I do believe though that the pressure is below specs. What can this do to a car? Could it cause a significant drop in mpg?
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Monday, July 28th, 2008 AT 8:51 AM

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