Symptom Definition

Fuel economy, as measured by an actual road test, is noticeably lower than expected. Fuel economy is noticeably lower than it was on this vehicle at one time.

Possible Cause & Correction - Check the following:

• Check for proper operation of thermostatic air cleaner damper door. Also check for a clogged air filter.
• Check cooling system thermostat for proper heat range and operation.
• Check coolant sensor for shift in calibration. Use temperature-to-resistance table in SENSOR RANGE CHARTS article.
• Ensure speedometer is properly calibrated.
• Check engine compression.
• Check for dragging brakes.
• Check A/C for "full time" operation.
• Ensure initial ignition timing is properly set and check for proper EST and ESC operation.
• Check for proper operation of TCC.
• Check air pump output not shifting to catalytic converter upon signal from TVS and/or faulty electrical and/or vacuum circuits.
• Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE CHECK in BASIC TESTING article.
• Check oxygen sensor for silicone or lead contamination.
• Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
• Check engine compression.
• Check for dragging brakes.