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 inspection. Refer to "SYSTEM DIAGNOSIS/PROCEDURES/CHECKING THE BASICS." Initial Inspection and Diagnostic Overview

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

^ 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?
- Air cleaner element for excessive dirt accumulation (restricted filter.)

IGNITION SYSTEM
^ CHECK:
- Spark plugs. Check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

COOLING SYSTEM
^ CHECK:
- Engine coolant level.

- CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.

ENGINE MECHANICAL
^ CHECK:
- Compression pressure.

ADDITIONAL CHECKS
^ CHECK:
- TCC operation. The engine speed display on a Tech-1 should indicate an RPM drop when the TCC is commanded "ON." Refer to "DIAGNOSTIC CHARTS/CHART C-8A, TORQUE CONVERTER CLUTCH (TCC) FUNCTIONAL CHECK."
- For exhaust system restriction. Refer to "DIAGNOSTIC CHARTS/CHART B-1, RESTRICTED EXHAUSTED SYSTEM CHECK." B Charts
- For proper calibration of speedometer.
- Induction system and crankcase for air leaks.