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 checks as described in Diagnosis By Symptom/Preliminary Checks. Testing and Inspection

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

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.
^ Engine thermostat for faulty part (always open) or for wrong heat range.

ENGINE MECHANICAL
Check compression.

ADDITIONAL CHECKS
Check:
^ [1][2]Torque Converter Clutch (TCC) operation. Use Chart C-8A Torque Converter Clutch Functional Check. The engine speed display on a Tech 1 should indicate a RPM drop when the TCC is commanded "ON." Chart C-8A Torque Converter Clutch (TCC) Functional Check

^ For exhaust system restriction. Use Restricted Exhausted System Check in B Chart B Charts

^ For proper calibration of speedometer.
^ Induction system and crankcase for air leaks.
^ Boost control system, use Chart C-18 Boost Control Solenoid Check. Chart C-18 Boost Control Solenoid Functional Check

^ Exhaust Gas Recirculation (EGR) valve for proper operation. Refer
to Chart C-7 Exhaust Gas Recirculation (EGR) Flow Check. Chart C-7 Exhaust Gas Recirculation (EGR) Flow Check