Poor Fuel Economy

SYMPTOM DESCRIPTION:

From an actual road test the measured M.P.G. is noticeably lower than expected. At one time the fuel economy for this vehicle was at a greater average than current measurement.

SYSTEM OR COMPONENT TO CHECK

FUEL
CHECK:
FUEL TYPE: quality and alcohol content.
FUEL PRESSURE: Check for restricted fuel return line or defective pressure regulator.
FUEL INJECTOR: Leaking or stuck injector
COLD START INJECTOR: Leaking or stuck

COMPUTER INPUTS/OUTPUTS
CHECK:
FUEL INJECTION CONTROL UNIT: Check for correct control unit
OXYGEN SENSOR: Perform CO test
AIR MASS METER: Defective sensor or wiring
COOLANT TEMPERATURE SENSOR: Not connected or faulty.

IGNITION
CHECK:
SPARK PLUGS: Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
IGNITION WIRES: For cracking, hardness, and proper connections.

COOLING
CHECK:
For obvious over heating problems.
FAN CLUTCH: Operation.
Low engine coolant level and leaks.
WATER PUMP: Loose belts?
Restricted air flow to radiator or restricted coolant flow.
THERMOSTAT: Faulty or incorrect.
Correct coolant solution - should be a 50/50 mix of anti-freeze (coolant) and water.

MECHANICAL - ENGINE/TRANSMISSION
CHECK:
Transmission shift pattern.
COMPRESSION:
Clutch slipping
For proper calibration of speedometer.
For dragging brakes.
For proper tire inflation.