GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Cavalier 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Poor Fuel Economy

Poor Fuel Economy

Checks

Action

DEFINITION: Fuel economy, as measured by an actual road test is noticeably lower than expected. Fuel economy is also noticeably lower than it was on the vehicle at one time, as previously shown by an actual road test.

Preliminary
    • Refer to Symptoms .
    • Search for service bulletins.
    • Check the owner's driving habits.
       - Is A/C ON full time, or is the defroster mode ON?
       - Are the tires at the correct pressure?
       - Are excessively heavy loads being carried?
       - Is the acceleration too much, too often?

Fuel System
    • Check the fuel pressure. Refer to Fuel System Diagnosis .
    • Check the fuel injectors. Refer to Fuel Injector Balance Test .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Ensure that each injector harness is connected to the correct injector/cylinder. Refer to Engine Controls Schematics .
    • Check for fuel in the pressure regulator vacuum hose.
    • Check for proper operation of the evaporative emission (EVAP) control system.

Sensor/System
    • Check the oxygen sensor (O2S 1). The O2S 1 should respond quickly to different throttle positions. If not, check the O2S 1 for silicon or other contaminants from fuel or from the use of an improper room-temperature vulcanizing (RTV) sealant. The sensors may have a white powdery coating indicative of silicon contamination, which may cause a high but false O2S 1 signal voltage, indicating a rich exhaust. The PCM will reduce the amount of fuel that is delivered to the engine, causing a severe driveability problem. Refer to Serial Data Communications .
    • Check for proper operation of:
       - The MAP sensor
       - The TP sensor
       - The ECT sensor

Ignition System
    • Check for proper ignition voltage output with the J 26792 spark tester or equivalent.
    • Check the spark plugs for the following conditions:
       - Wet or fuel-fouled spark plugs
       - Cracks on the spark plugs
       - Wear
       - Improper spark plug gap
       - Burned electrodes or heavy deposits
    • If the spark plugs are fuel or oil-fouled, determine the cause of the fouling before replacing the spark plugs.
    • Check the ignition control module (ICM) for proper ground connection.
    • Check the ignition coils for cracks or carbon tracking.
    • Check the spark plug wires for proper resistance and condition.

Engine Cooling System
    • Check engine coolant level for being low. Refer to Loss of Coolant in Engine Cooling.
    • Check for incorrect or malfunctioning engine thermostat. Refer to Engine Coolant Thermostat Replacement in Engine Cooling.

Engine Mechanical
    • Check engine mechanical for the following:
       - Compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Bent push rods
       - Worn rocker arms
       - Broken valve springs
       - Excessive oil in the combustion chamber-leaking valve seals.
    • Check the engine for incorrect basic engine parts. Inspect for the following:
       - Camshaft
       - Cylinder heads
       - Pistons
       - Other engine parts as appropriate
    • Refer to Base Engine Misfire Diagnosis in Engine Mechanical.

Additional Checks
    • Check the torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Transmission/Transaxle.
    • Check the exhaust system for possible restrictions. Check for the following:
       - Inspect the exhaust system for damaged or collapsed pipes.
       - Inspect the mufflers for heat distress or possible internal failure.
       - For possible plugged three-way catalytic converter. Refer to Restricted Exhaust and/or Exhaust System.