Fuel Economy Poor

DEFINITION:
Fuel economy as measured by an actual road test, is noticeably lower than expected. Or, economy is noticeably lower than it was on this car at one time, as previously shown by an actual road test.

Check Powertrain System, if not already completed


Check for the following mechanical causes:
- Dragging Brakes
- Low Engine Compression
- Low Tire Pressure
- Air Induction Restrictions
- Vacuum Leaks in Intake Manifold System


Check for possible driver-induced causes:

- A/C "ON" at All Times
- Vehicle Used Only for Short Trips (Engine Never Warms Up)
- Fuel Economy Calculated Incorrectly
- Vehicle Regularly Carries a Heavy Load
- Driving Habits (Lead Foot)
- Driving in D3, D2, or D1



Check EGR System.


Check Exhaust, looking in particular for:

- Restricted Catalytic Converter or Exhaust



Check Ignition System, looking in particular for:

- High Resistance, Open, Shorted, or Arcing Spark Plug Wires, crossfire between spark plug wires

- Contaminated or Damaged Spark Plugs


Check Fuel System, looking in particular for:

- Fuel Quality
- Alcohol Content Contaminants
- Water Content
- Sour Fuel

- Incorrect Fuel Pressure

- Fuel injectors:
- Leaking
- High Flow Rate