GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 Park Avenue 🢒 Engine 🢒 Engine Electrical 🢒 Poor Fuel Economy

Checks

Action

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
    • Refer to Important Preliminary Checks in Symptoms - Engine Controls .
    • Refer to Visual/Physical Checks in Symptoms - Engine Controls .
    • Search for bulletins.
    • Check owners driving habits.
       - Is A/C ON full time, defroster mode ON?
       - Are tires at correct pressure?
       - Are excessively heavy loads being carried?
       - Is owner accelerating 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 with Special Tool and Fuel Injector Balance Test with Tech 2 .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Ensure each injector harness is connected to the correct injector/cylinder.
    • Check for fuel in the pressure regulator vacuum hose.

Sensor/System
    • Check air intake system and crankcase for air leaks. Refer to Air Intake System Description .
    • Check for proper calibration of speedometer. Connect J 33431-C Signal Generator to vehicle speed sensor (VSS) electrical connector. Turn ON the ignition and tester, monitor the speedometer.

Ignition System
    • Check for proper ignition voltage output using the following steps:
       - Clip the J 26792 Spark Tester to engine ground.
       - Connect one end of a spark plug wire to the spark tester. Leave the other end of the spark plug wire connected to the coil being tested.
       - Connect another spark plug wire between the remaining tower of the coil being tested and ground.
       - Crank the engine while observing the spark tester, a crisp blue spark should be observed.
       - Repeat the above steps for each coil.
    • If adequate spark is not present at the coils, check for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and its mate.

       - Coils--Cracks, carbon tracking/arcing, or a resistance value outside the specified range.

Coil Resistance
5,000-8000 ohms

       - Spark plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range.

Spark Plug Wire Resistance
9,840 ohms per meter (3,000 ohms per ft)

   Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. Ignition components will arc to ground when a secondary component is faulty.

       - Defective module.
       - Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove spark plugs and check for the following:
       - Fouled plugs
       - Cracks

   Important: If carbon tracking is detected on a component, replace that component and its mate.

       - Check the spark plugs for carbon tracking on the porcelain and pitting on the plug wire contact.
       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach
       - Refer to Maintenance Items in Maintenance and Lubrication.
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

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

Engine Mechanical
    • Check engine mechanical for the following:
       - Check compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Bent push rods
       - Worn rocker arms
       - Broken valve springs
       - Excess oil in combustion chamber-Inspect for leaking valve seals.
    • Inspect for incorrect engine parts, such as the following basic components:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures.

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