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 vehicle at one time, as previously shown by an actual road test.

POWERTRAIN SYSTEM CHECK
Perform Chart 1: Powertrain System Check. 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

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 (EGR) SYSTEM CHECK
Perform Chart 6EC-2 EGR System Check. Chart 6EC-2 EGR System Check

EXHAUST SYSTEM
Perform exhaust diagnosis looking in particular for:

^ Restricted catalytic converter or exhaust

IGNITION SYSTEM CHECKS
Perform Chart C-1 Ignition Control Performance Test. Check in particular for:

^ High resistance, open, shorted, or arcing spark plug wires, crossfire between spark plug wires
^ Contaminated or damaged spark plugs
^ Correct ignition timing

C Charts

FUEL SYSTEM CHECK
Perform Chart 6C-1 Fuel System Check. Check 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