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
Perform the careful visual and physical checks as described in Preliminary Checks.

^ Check air cleaner element (filter) for dirt or being plugged.

^ Visually (physically) check: Vacuum hoses for splits, kinks, and proper connections as shown on "Vehicle Emission Control Information" label.

^ Perform On-Board 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?

NOTE: 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 pressure. Refer to Chart A-7 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: Knock Sensor operation. Refer to Chart C-5 Knock Sensor (KS) System Check. Chart C-5 Knock Sensor (KS) System Check

Check: Ignition timing. Refer to underhood "Vehicle Emission Control Information" label.

COOLING SYSTEM
Check: Engine coolant level.

Check: Engine thermostat for faulty part or for wrong heat range.

ADDITIONAL CHECKS
Check: TCC operation - Refer to Chart C-8 Torque Converter Clutch (TCC) System. A scan tool should indicate a RPM drop when the TCC is commanded "ON." Chart C-8 Torque Converter Clutch (TCC) Diagnosis

Check: For proper calibration of speedometer.

Check: For dragging brakes.