GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 S10 Pickup - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Hesitation, Sag, Stumble

Inspection/Tests

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. May cause the engine to stall if severe enough.

Preliminary
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Engine Controls Schematics .

Sensor/System
    • Inspect the manifold absolute pressure (MAP) sensor operation.
    • Inspect the oxygen sensor (O2S) 1. The O2S 1 should respond quickly to different throttle positions. If not, inspect 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, a rich exhaust indication. The powertrain control module (PCM) will reduce the amount of fuel delivered to the engine, causing a severe driveability problem.
    • Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0105 .
    • Inspect for proper operation of the throttle position (TP) sensor. Refer to DTC P0105 .
    • Inspect for proper operation of the engine coolant temperature (ECT) sensor. Refer to Temperature Versus Resistance .

Fuel System
    • Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect 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 fuel injectors. Refer to Fuel Injector Solenoid Coil Test and Fuel Injector Balance Test with Tech 2 .
    • Inspect for the following that may cause the engine to run rich:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Water intrusion in the HO2S connector
       - Engine oil contaminated by fuel
       - An EVAP canister purge condition
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - A leaking fuel pressure regulator--Refer to Fuel System Diagnosis .
       - Leaking fuel injectors--Refer to Fuel System Diagnosis .
       - Any vacuum hoses that are split, kinked, or improperly connected
       - An air intake duct that is collapsed or restricted
       - An air filter that is dirty or restricted--Refer to Air Cleaner Element Replacement .
    • Inspect for the following conditions that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
       - Vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel System Diagnosis .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Ignition System
    • Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
    • Test for proper ignition voltage output with the J 26792 Spark Tester . Refer to Electronic Ignition (EI) System Diagnosis for the procedure.
    • Remove the spark plugs and check for the following:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits

Refer to Spark Plug Inspection .

    • An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .
    • Determine the cause of the fouling before replacing the spark plugs.
    • Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
    • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Cooling System

Inspect the engine thermostat for proper operation and for proper heat range. Refer to Thermostat Diagnosis in Engine Cooling.

Additional Inspections
    • Inspect the generator output voltage. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical for the procedure. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.
    • Inspect for proper operation of the automatic transmission.