Poor Fuel Economy

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.

POWERTRAIN SYSTEM
Perform Powertrain System Check, if not already completed. Chart 1 Powertrain System Check

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

DRIVER-INDUCED CAUSES
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

EXHAUST GAS RECIRCULATION
Check EGR System. Refer to Chart 6EC-1 EGR System Check. Chart 6EC-1 EGR System Check

EXHAUST DIAGNOSIS
Check exhaust system looking In particular for:

^ Restricted Catalytic Converter or Exhaust

IGNITION SYSTEM
Perform Chart 1 Ignition System Check, looking in particular for:

^ High Resistance, Open, Shorted, or Arcing Spark Plug Wires, crossfire between spark plug wires
^ Contaminated or Damaged Spark Plugs

Chart 1 Ignition System Check

FUEL SYSTEM
Perform Chart 6C-1 Fuel System Check looking in particular for:

^ Fuel Quality
- Alcohol Content
- Contaminants
- Water Content
- Sour Fuel
^ Incorrect Fuel Pressure
^ Fuel Injectors
- Leaking
- High Flow Rate

Chart 6C-1 Fuel System Check