GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1999 🢒 Shelby Series 1 🢒 Engine 🢒 Engine Controls - 4.0L 🢒 Surges/Chuggles

Checks

Action

DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal position.

Preliminary
    • Refer to Important Preliminary Checks Before Starting in Symptoms .
    • Search for bulletins.
    • Inspect the PCM grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .

Sensor/System
    • Test the heated oxygen sensors (HO2S). The HO2S should respond quickly to the different throttle positions. If they do not, inspect the HO2S for silicon or other contaminates from fuel or the use of improper RTV sealant. The sensors may have a white powdery coating and result in a high but false signal voltage (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. For more information, refer to Information Sensors/Switches Description .
    • Inspect the MAF sensor connections. Repair or replace the terminals. Refer to Connector Repairs in Wiring Systems.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect that each injector harness is connected to the correct injector or cylinder according to the firing order. Relocate injector harnesses as necessary.
    • Test 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 .
    • Test 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 .

Ignition System
    • Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water.
    • Test for proper ignition voltage output with J 26792 spark tester. Refer to Electronic Ignition (EI) System Diagnosis .
    • 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 causes a driveability condition. 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 DTC P0172 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of the rich condition. Refer to 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 132°C (270°F). This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the PCM turns fuel off to four cylinders at a time in order to keep engine temperatures from reaching damaging levels. The system perceives Engine Coolant Over Temperature-Fuel Disabled Mode as a lack of power, a miss, or a rough idle. If the vehicle operates in Engine Coolant Over Temperature-Fuel Disabled Mode, refer to Engine Overheating for diagnosis.

Additional Checks

Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label. Refer to Emission Hose Routing Diagram .