Poor Fuel Economy

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

PRELIMINARY CHECKS
Refer to Important Preliminary Checks. Testing and Inspection
Check air cleaner element (filter) for dirt or being plugged and operation of thermostatic air cleaner.
Visually (physically) check Vacuum hoses for splits, kinks, and proper connections as shown on "Vehicle Emission Control Information" label.
Perform Diagnostic System Check Testing and Inspection
Check owner's driving habits.
- Is A/C "ON" full time (Defroster mode "ON")?
- Are tires at correct pressure?
- Are excessively heavy loads being carried?
- Is acceleration too much, too often?
Suggest driver read "Important Facts on Fuel Economy" in Owner's Manual.
Check for fuel leaks.

FUEL SYSTEM
CHECK: Fuel type, quality and alcohol content. Refer to Fuel Delivery and Air Induction/Testing and Inspection/Procedures/Alcohol-In-Fuel Test Alcohol/Contaminants-In-Fuel Testing Procedure
CHECK: Fuel pressure. Refer to Diagnostic Charts/Chart A-6 Fuel System Diagnosis. Related Tests, Information and Procedures

IGNITION SYSTEM
CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
CHECK: Ignition wires for cracking, hardness, and proper connections.
CHECK: KS system operation.
CHECK: Ignition timing.

COOLING SYSTEM
CHECK: Engine coolant level.
CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.

ADDITIONAL CHECKS
CHECK: Transmission shift pattern.
CHECK: TCC operation - A scan tool should indicate an RPM drop when the TCC is commanded "ON."
CHECK: For proper calibration of speedometer.
CHECK: For dragging brakes.
CHECK: Compression.