DIAGNOSING POOR FUEL ECONOMY
by Mark Davidson
The vehicle runs normally however, fuel economy is lower than it was at one time. If the vehicle runs poorly refer to the specific running symptom for further diagnostic information. Any running or performance problems should be diagnosed prior to using this symptom’s diagnosis.
Poor fuel economy can be caused by a multitude of problems. Driving habits and enviroments play a significant role in fuel economy. Prior to diagnosing this symptom, you should drive for at least two full tanks of gas to ensure there is a problem rather than an intermittent condition, such as mountainous driving. Poor fuel economy is usually the result of lack of routine maintenance.
You should start your diagnosis by determining what service has been performed on the vehicle. Routine spark plug replacement is necessary to maintain good fuel economy. Spark plugs provide the ignition source to initiate the combustion process to burn the fuel. If the spark plugs are worn they will not provide a good ignition source for the fuel and can degrade the fuel economy. The air filter filters the air that enters the engine. It is designed to remove the harmful dust and debris that would otherwise enter the engine. An air filter that is only partially plugged can restrict the air entering the engine and reduce the fuel economy. Inspect the air filter and replace it even it is only moderately dirty. A new filter can go a long way in improving fuel economy. Do not attempt to blow out the filter with compressed air. New filters rely on small fibers to “grab” the incoming dirt particles. Blowing out the filter will remove these fibers and reduce the filters affectiveness. Tire inflation should be checked. Low tire pressure can reduce fuel economy drastically. Tires provide the necessary traction to prevent the vehicle from skidding and slidding. At the same time, tires provide a low rolling resistance so that the engine can easily propel the vehicle. If the tires are low, the rolling resistance is increased and will require the engine to consume more fuel to generate the same amount of power. You should ensure the tires are inflated evenly and to the proper pressure. Proper ignition timing is critical to maintain good fuel economy. Most newer vehicles have computer controlled ignition timing. On these systems, the timing is not adjustable. On vehicles that have adjustable ignition timing the timing should be checked. You should consult the underhood emission control label for instructions on ignition timing adjustments. Engine oil can also affect your vehicles fuel economy. You should ensure you are using a multi-viscosity oil as recommended by your vehicles manufacturer.
PRECAUTIONS, TIPS, and NOTES
Consult your owners manual for recommended service intervals and maintenance schedules for your driving conditions. Also refer to the “Vehicle Maintenance Tips” article for more information on preventative maintenance.
gave up on sports when the Browns left Cleveland and now spends his
Sundays working under a shade tree in the back yard tuning his son’s
soap box derby car.)
Gas tank will not except feel fast very slow think it’s a clog vent line 05 Chevrolet 2500 HD 6 L
Always check the basics and diagnose and performance issues first like Mark said.
If all is okay have your technician hook up the diagnostic tool and check parameters to see whats out of whack, lazy oxygen sensor, fuel trim way off base or out of line.
Then get the carbon cleaned out with a good complete fuel system cleaner. It will get the carbon off the valves, oxygen sensors, catalytic converter, ect.
It will allow your engine to breath again just like if your nose was clogged.
Hope this helps
Mark Hank White
What do you guys think about using acetone in the gas at a rate of 1 oz per gallon. I did it in my honda civic hatchback for year and i got really good gas mileage. Its supposed to evaporate quicker in the chamber and burn more efficiently. I saw tests of the fuel lines and fuel injector orings soaked in acetone and they were fine.
I have a 2016 dodge jorney with 2.4 its got 7000 miles when I got it gave me 29 mpg now its giving me 21 ????? everthing is new what could b the problem??????????????
Hi i have a fuel problem. I have a manual toyota 2000 rav4 2l. When i go through the gears its loses power and shudders- power then no power.
I have had it serviced and the spark plugs changed.and it still does it and its worse, also had the fuel filter changed and it still the same.
I live in the Middle East and drive a Pathfinder SE 2010. My fuel consumption has been really low since couple of years. Last week I got the spark plugs changed, engine tune up done, air filter replaced and the injector cleaned; but still no difference. I used to get about 525 kms on a full tank but now it barely makes it to 350. This is a huge difference. The Garage I gave to is a reputed one but they say they can find no other fault. Will it take time for the difference to be noticed since I have done the repairs not too long ago?