Hesitation, Sag, Stumble

WARNING: This page is about a different variant/trim than selected.

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. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
Sensor/System	NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Any water intrusion in the heated oxygen sensor (HO2S) connector The engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure-Refer to Fuel System Diagnosis . Any 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: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Any water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Any vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Any restricted fuel injectors-Refer to Fuel Injector Balance Test with Tech 2 . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) . Any vacuum hoses that are split, kinked, or improperly connected Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 . Inspect for proper operation of the engine coolant temperature (ECT) sensor. Refer to Temperature vs Resistance .
Fuel System	Test 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 (without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) . Test the fuel injector Refer to Fuel Injector Coil Test .
Ignition System	In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Remove spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Verify that the spark plugs are of the correct type. Inspect for proper ignition voltage output with the J 26792 HEI Spark Tester.Special Tools . An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. Determine the cause of the fouling before replacing the spark plugs. Inspect for damaged or misaligned spark plug boots. Inspect the electronic ignition (EI) module for proper ground connection. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
Engine Cooling System	Inspect the engine thermostat for proper operation and for correct heat range. Refer to Thermostat Diagnosis in Engine Cooling.
Engine Mechanical	Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start to stall Erratic performance