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
1. Perform careful visual and physical checks as described in preliminary checks. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnosis by Symptom / Preliminary Checks. Testing and Inspection
2. Visually (physically) check: Vacuum hoses for splits, kinks, and proper connections as shown on "Vehicle Emission Control Information" label.
3. 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?
4. Check for a dirty or plugged air cleaner. Also check for fuel leaks.

ADDITIONAL CHECKS
1. Check the [1][2]Torque Converter Clutch (TCC) operation. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart C-8A. Chart C-8A Torque Converter Clutch (TCC) Diagnosis
A Tech 1 scan tool should indicate an RPM drop, when the TCC is commanded "ON."
2. Check for exhaust system restriction. Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Charts / Chart B-1.B Charts
3. Check for proper calibration of speedometer.
4. Check the induction system and crankcase for air leaks.

IGNITION SYSTEM
Check the spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

COOLING SYSTEM
1. Check the engine coolant level.
2. Check the engine thermostat for faulty, part (always) open or for wrong heat range.

ENGINE MECHANICAL
Check the compression.