Poor Fuel Economy

SYMPTOM 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 Diagnostic Notes. Initial Inspection and Diagnostic Overview
^ 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 Circuit 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 owner fill fuel tank and recheck fuel economy.
^ Suggest driver read "Important Facts on Fuel Economy" in Owner's Manual.

FUEL SYSTEM
Check:
^ Fuel type, quality and alcohol content.
^ Fuel pressure. Refer to "Chart A-6." 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.
^ Ignition wires for cracking, hardness, and proper connections.
^ KS system operation.
^ Ignition timing.

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

ADDITIONAL CHECKS
Check:
^ Transmission shift pattern.
^ TCC operation - A scan tool should indicate a rpm drop when the TCC is commanded "ON."
^ For proper calibration of speedometer.
^ For dragging brakes.