Lack of Power, Sluggishness, or Sponginess

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

Inspection/Tests	Action
DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.
Preliminary Inspections	Refer to Important Preliminary Inspections Before Beginning 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 . Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement and replace as necessary.
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 injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , or Fuel Injector Coil Test . 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. Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister 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 . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted - Refer Air Cleaner Outlet Resonator Replacement . 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: Water intrusion in the HO2S connector NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. 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 Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected
Sensor/System	Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Scan Tool Data List .
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 Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester. See Special Tools . An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection . 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 . 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 the water.
Engine Mechanical	Inspect for incorrect camshaft timing. Inspect for excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. Test the cylinder compression. Refer to Engine Compression Test in Engine Mechanical. Inspect for incorrect, worn, or damaged basic engine parts, including the following: The camshaft - Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in 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 and stall Erratic performance
Additional Inspections	Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust. Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or internal failure. Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission - 4L60-E/4L65-E.