GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Lack of Power, Sluggishness, or Sponginess

Checks

Action

DEFINITION: The engine delivers less than expected power. Little or no increase in the speed when the accelerator pedal is pushed down part of the way.

Preliminary Checks
    • Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .
    • Refer to visual checks and physical checks in Symptoms - Engine Controls .
    • Search for bulletins.

Fuel System
    • Check the fuel pressure.
       - Refer to Fuel System Diagnosis .
       - Refer to Engine Oil Pressure Sensor and/or Switch Replacement in Engine Mechanical.
    • Check the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check items which can cause an engine to run rich. Refer to DTC P0172 .
    • Check items that can cause an engine to run lean. Refer to DTC P0171 .

Sensor/System
    • Use a scan tool in order to monitor the knock sensor system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .
    • Check the EGR valve for a stuck open pintle. Refer to Exhaust Gas Recirculation Valve Replacement .
    • Check for a restricted intake duct or for a dirty air cleaner element. Refer to Air Cleaner Element Replacement .

Ignition System
    • Check for proper ignition voltage output using the following steps:
       - Attach the J 26792 Spark Tester to engine ground.
       - Connect one end of a spark plug wire to the J 26792 . Connect the other end of the spark plug wire to the coil that is being tested.
       - Connect another spark plug wire between the remaining tower of the coil that is being tested and the ground.
       - Crank the engine, and observe the J 26792 . A spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the plugs, check for the following conditions:

   Important: If you detect carbon tracking on a component, replace that component and the component's respective match.

       - Inspect the coils for cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

Secondary Coil Resistance
5K-8K ohms (5,000-8,000 ohms)

       - Inspect the spark plug wires for the following conditions: cracks, any arcing, incorrect firing, incorrect routing, carbon tracking, plug boot damage, pinched, or a resistance value more than the specified value.

Spark Plug Wires Resistance
1000-1500 ohms/ft

   Important: Spraying the secondary ignition wires with a small amount of water may help locate an intermittent condition. Ignition components will arc to ground if a secondary component is malfunctioning.

       - Check the ignition control module for a malfunction.
       - Check the ignition system wiring for a loose ignition module feed, a bad ground connection, or for a damaged wiring system .
    • Remove the spark plugs.
    • Inspect the spark plugs for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and the component's match.

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

Engine Mechanical
    • Check for excess oil in the combustion chamber, and inspect for leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • Inspect for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    • Refer to the appropriate misfire procedures in Engine Mechanical. Inspect for incorrect engine parts, such as the following basic components:
       - The camshaft
       - The cylinder heads
       - The pistons

Additional Checks
    • Check the exhaust system for a possible restriction.
       - Inspect the exhaust system for damaged pipes or for collapsed pipes.
       - Inspect the muffler for heat damage or for an internal condition.
       - Check for a plugged three-way catalytic converter. Refer to Restricted Exhaust in Engine Exhaust.
    • Check for the torque converter clutch (TCC) operation. Refer to Diagnostic Starting Point - Automatic Transmission in Automatic Transaxle.