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Makes 🢒 Oldsmobile 🢒 2002 🢒 Alero 🢒 Engine 🢒 Engine Electrical 🢒 Rough, Unstable, or Incorrect Idle and Stalling

Rough, Unstable, or Incorrect Idle, Stalling

Checks

Action

DEFINITION: The engine runs unevenly during idle. If the condition is severe, the engine or the vehicle may shake. The engine idle speed can vary in RPM. Either condition can be severe enough to stall the engine.

Preliminary Checks
    • Refer to Symptoms - Engine Controls .
    • Search the service bulletins.

Fuel System

Check the following components:

    • The fuel system pressure--Refer to Fuel System Diagnosis .
    • The fuel injectors--Refer to Fuel Injector Solenoid Coil Test .
    • The fuel--Check for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • The fuel filter--Check for plugs or for restrictions.
    • Conditions which can cause the engine to run rich, indicating that the long term fuel trim is significantly in the negative range--Refer to Diagnostic Aids for DTC P0172 .
    • Conditions that can cause the engine to run lean, indicating that the long term fuel trim is significantly in the positive range--Refer to Diagnostic Aids for DTC P0171 .
    • The evaporative emission (EVAP) control system--Check for correct operation. Refer to Evaporative Emission Control System Description .
    • Check for fuel in the fuel pressure regulator vacuum hose.

Sensor/System

Check the following components for proper operation:

    • The manifold absolute pressure (MAP) sensor. Refer to DTC P0105 .
    • The throttle position (TP) sensor. Refer to DTC P0105 .
    • The idle air control (IAC) motor. Refer to Idle Air Control (IAC) System Diagnosis .
    • The engine coolant temperature (ECT) sensor. Refer to DTC P0117 and DTC P0118 .
    • The oxygen sensor (O2S 1)--The O2S 1 should quickly respond to the different throttle positions. If the sensor does not respond, check the sensor for silicon, or other contaminants from fuel or from the use of an improper RTV sealant. The sensor may have a white powdery coating. Silicon contamination causes a high but false O2S 1 signal voltage, indicating a rich exhaust indication. The powertrain control module (PCM) will reduce the amount of fuel that is delivered to the engine, causing a severe driveability problem.

Ignition System
    • Check for proper ignition voltage output. Use the J 36012-A Ignition System Diagnostic Harness and use the J 26792 Spark Tester or equivalent.
    • Check the spark plugs for the following conditions:
       - Wet spark plugs
       - Fuel-fouled spark plugs
       - Cracked spark plugs
       - Worn spark plugs
       - Improper spark plug gap
       - Burned electrodes
       - Heavy deposits
    • If the spark plugs are fuel or oil-fouled, determine the cause of the fouling before you replace the spark plugs.
    • Check the ignition control module (ICM) for proper ground connection.
    • Check the ignition coils for cracks or for carbon tracking.

Engine Mechanical

Check the following components or conditions for proper operation:

    • The compression
    • Sticking vales
    • Leaking valves
    • Worn camshaft lobes
    • The valve timing
    • Broken valve springs
    • Weak valve springs
    • The balance shaft for:
       - Damage
       - Incorrect installation
    • Excessive oil in the combustion chamber, caused by leaking valve seals
    •  Inspect the following components for incorrect basic engine parts:
       - The camshafts
       - The cylinder head
       - The pistons
    • Refer to Symptoms - Engine Mechanical in Engine Mechanical 2.2 L (L61).

Additional Checks

Check the following components for the following conditions:

    • The exhaust system:
       - Inspect for damaged pipes and for collapsed pipes.
       - Inspect the mufflers for heat distress and for internal failure.
       - Inspect the 3-way catalytic converter for plugs. Refer to Restricted Exhaust in Engine Exhaust.
    • Check for proper operation of the crankcase ventilation system.
    • Check for malfunctioning engine mounts. Refer to Symptoms - Engine Mechanical in Engine Mechanical 2.2 L (L61).
    • Electromagnetic interference (EMI) can cause an engine miss condition on the reference circuit. You can usually detect EMI can by monitoring the engine RPM with a scan tool. A sudden increase in the RPM, with little change in the actual engine RPM change indicates that EMI is present. If a problem exists, check the routing of the secondary ignition wires and check the high voltage components, located near the ignition control circuits.