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 / physical checks as described in Preliminary Checks.
^ Check air filter for dirt or being plugged and the operation of the Thermostatic Air Cleaner (TAC).
^ Visually (physically) check: Vacuum hoses for splits, kinks, and proper 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?
^ Suggest owner fill tank and recheck fuel economy.
^ Suggest driver read "Important Facts on Fuel Economy" in owners manual.

FUEL SYSTEM
^ Check fuel type, quality and alcohol content.
^ Check fuel pressure, refer to Procedures / Diagnostic Charts / Chart A-6 Fuel System Diagnosis. Testing and Inspection

IGNITION SYSTEM
^ Check the 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 (KS) system operation, refer to Procedures / Diagnostic Charts / C Charts / Knock Sensor (KS) System. Testing and Inspection
^ 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 [1][2]Torque Converter Clutch (TCC) operation. The engine speed display on a Tech 1 should indicate an RPM drop when the TCC is commanded "ON."
^ Check for proper calibration of speedometer.
^ Check for dragging brakes.