Poor Fuel Economy

If fuel economy is lower than expected during a road test, or has decreased since previous road tests, check the following items:

• Ensure idle speed is correct.
• Ensure air intake system is unrestricted.
• Ensure fuel system pressure is correct. Use ohmmeter to verify correct fuel injector resistance.
• Check canister purge control valve operation.
• Ensure engine has sufficient compression.
• Ensure correct throttle position sensor or throttle switch adjustment and resistance value.
• Check operation of coolant temperature sensor.
• Check for excessive timing retard due to high level of carbon build-up.
• Check EGR valve and solenoid for correct operation.
• Check for poor quality or contaminated fuel. Check for fuel with high alcohol content.
• Ensure spark plug application is correct.
• Ensure exhaust system is unrestricted.
• Check MAT sensor signal.
• Verify brakes are not dragging.
• Check for faulty ECM.