GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Sonoma Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L (L43) 🢒 Hesitation, Sag, Stumble

Checks

Action

DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.

Preliminary
    • Refer to Symptoms .
    • Search for service bulletins.

Sensor/System
    • Check the oxygen sensor (O2S 1). The O2S 1 should respond quickly to different throttle positions. If not, check the O2S 1 for silicon or other contaminants from fuel or the use of improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false O2S 1 signal voltage (rich exhaust indication). The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
    • Check for proper operation of the MAP sensor. Refer to Manifold Absolute Pressure Sensor Output Diagnosis .
    • Check for proper operation of the TP sensor.
    • Check for proper operation of the ECT sensor.

Fuel System
    • Check the fuel pressure. Refer to Fuel System Diagnosis .
    • Check the injectors. Refer to Fuel Injector Balance Test .
    • Check items which can cause an engine to run rich--the Long Term FT is significantly in the negative range. Refer to Diagnostic Aids for DTC P0172 Fuel Trim System Rich .
    • Check items that can cause an engine to run lean--Long Term FT is significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 Fuel Trim System Lean .
    • Check for proper operation of the evaporative emission (EVAP) control system.

Ignition System
    • Check for proper ignition voltage output with the spark tester J 26792 or equivalent.
    • Check the spark plugs for the following conditions:
       - Wet or fuel fouled
       - Cracks on the spark plugs
       - Wear
       - Improper spark plug gap
       - Burned electrodes or heavy deposits
    • Use the scan tool in order to monitor the cylinder misfire screen to aid in pinpointing a specific cylinder fault.
    • If the spark plugs are fuel or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Check the ignition control module (ICM) for proper ground connection.
    • Check the ignition coils for cracks or carbon tracking.
    • Check the spark plug wires for proper resistance and condition.

Additional Checks
    • Check for proper operation of the Automatic Transmission.
    • Check the generator output voltage. Repair the generator if the output voltage is less than 11.0 volts or more than 16.0 volts.
    • If all procedures have been completed and no malfunctions have been found, review and inspect the following items:
       - All electrical connections within the suspected circuit and/or systems.
       - Scan tool data.
       - If the Short Term FT is attempting to lean an engine with a rich condition--the negative fuel trim numbers are above 20--hesitation on tip in throttle is usually the result.