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For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1999 🢒 Shelby Series 1 🢒 Engine 🢒 Engine Controls - 4.0L 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

Checks

Action

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

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Starting in Symptoms .
    • Search for bulletins.
    • Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .
    • Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Filter Element Service and replace as necessary.

Fuel System
    • Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.
    • Test for proper fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the items which can cause an engine to run rich. For a rich condition, refer to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 and DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1 .
    • Inspect the items that can cause an engine to run lean. For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Sensor/System

Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .

Ignition System
    • Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuit and the injector circuits for an intermittent short to ground.
    • Wet down the secondary ignition system with water from a spray bottle. Wetting the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied.
    • Test for proper ignition voltage output with J 26792 spark tester.
    • Remove the spark plugs and inspect for the following conditions:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • An improper spark plug gap will cause a driveability concern. Gap the spark plugs using a wire gauge gap tool.
    • Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to the following procedures:
       -  DTC P0172 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of a rich condition
       - Spark Plug Visual Diagnosis for diagnosis of coolant or oil fouled spark plugs
    • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Mechanical
    • Ensure that the engine coolant temperature is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel Disabled Mode. While in Engine Coolant OverTemperature-Fuel Disabled Mode, the PCM will turn the fuel off to 4 cylinders at a time to keep engine temperatures from reaching damaging levels. The system perceives the Engine Coolant OverTemperature-Fuel Disabled Mode as a lack of power, miss, or rough idle. If the vehicle operates in Engine Coolant Over Temperature-Fuel Disabled Mode, refer to Engine Overheating.
    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis.
    • For incorrect basic engine parts, inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to the appropriate procedures in Engine Mechanical.

Additional Inspections

Inspect the following exhaust system components for possible restrictions:

    • The exhaust system for physical damage
    • The exhaust manifold for a collapsed inner wall
    • The mufflers for heat distress or possible internal failure
    • The three-way catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine