Poor Fuel Economy

SYMPTOM DESCRIPTION
From an actual road test the measured MPG 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 ACTION

FUEL CHECK FUEL TYPE, quality and alcohol content
Alcohol/Contaminants-In-Fuel Testing Procedure
FUEL PRESSURE
Related Tests, Information and Procedures




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.
ESC operation.
Knock Sensor
TIMING.



COOLING CHECK Overheating problems
- Low engine coolant level and leaks.
- Water pump operation, loose belts
- Restricted air flow to radiator or
restricted coolant flow.
- Faulty or incorrect thermostat.
- Correct coolant solution - should be a 50/50
mix of anti-freeze (coolant) and water.
- Fan operation.
Insufficient temperature
- Thermostat faulty (always open) or wrong heat range.






ENGINE/TRANSMISSION CHECK - Transmission shift pattern.
- TCC operation. A "Scan" tool should indicate an
rpm drop when the TCC is commanded "ON."
- Proper calibration of speedometer.
- Dragging brakes.
- Proper tire inflation.