Symptoms Testing

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

Backfire, Cuts Out/Misses, Detonation/Spark Knock, Dieseling/Run-On, Engine Control Module (ECM) Commanded Reduced Engine Power, Fuel Odor, Hard Start, Hesitation/Sag/Stumble, Lack of Power/Sluggishness/Sponginess, Poor Fuel Economy, Rough, Unstable, or Incorrect Idle and Stalling, or Surges/Chuggles

Test/Inspect the fuel system for the conditions listed below:
- Incorrect system operation or fuel pressure-Refer to Fuel System Diagnosis (LSA) .
- Leaking or incorrectly operating fuel injectors-Refer to Fuel Injector Diagnosis (LSA) .
- Contaminated or poor quality fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Test/Inspect the ignition system for the conditions listed below:
- Spark plugs with incorrect heat range or an abnormal condition-Refer to Spark Plug Inspection , and Ignition System Specifications .
- Coolant or oil fouled spark plugs. For diagnosis, refer to Coolant in Combustion Chamber , or Oil Consumption Diagnosis .
- Secondary ignition system susceptible to moisture. Engine running, wet down the secondary ignition system with water from a spray bottle to help locate damaged or deteriorated components. Look/listen for arcing or misfiring as the water is applied.
- Weak spark using the J 26792 spark tester -Refer to Electronic Ignition System Diagnosis .
Test/Inspect the supercharger system for the conditions listed below:
- Damaged, worn or misaligned supercharger belt and belt tensioner. Repair or replace only if necessary.
- Excessively worn, loose, or damaged components
- Sticking or binding components
- Leaking supercharger intake manifold and plenum gaskets and seals
- Split, kinked, or incorrectly connected vacuum hoses
- Incorrectly operating supercharger intercooler pump or pump relay. Refer to Supercharger Intercooler Relay Diagnosis .
- Excessive noise. Operate the vehicle at idle and at various stages of acceleration and compare the supercharger noise levels to those heard while operating a comparable vehicle at comparable conditions. For an explanation of typical supercharger system noises, refer to Supercharger Noise Diagnosis .
- Incorrect operation-Refer to Supercharger Description and Operation , Boost Control System Description , and Boost Control System Diagnosis for additional information.
Inspect for the conditions listed below:
- Non-metered air flow into the air induction system. If a leak is found, repair as necessary. The Q38 Throttle Body: Throttle/Idle Learn procedure must be performed when the repair is complete.
- Incorrectly operating transmission torque converter clutch-The scan tool should indicate an engine speed drop when the torque converter clutch is commanded ON. Refer to Torque Converter Diagnosis .
- Incorrectly operating A/C compressor
- Items that can cause an engine to run rich or lean.
- Slow responding heated oxygen sensors. The heated oxygen sensors should respond quickly to different throttle positions.
- Water intrusion in the heated oxygen sensors connector
- Incorrect mass airflow sensor installation. A mass airflow sensor that is incorrectly installed may cause a hard start. Install the mass airflow in the correct direction. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (LSA) .
- Incorrect mass airflow sensor connections.
- Engine oil contaminated by fuel
- Split or kinked vacuum hoses-Verify that the routing and connections are as shown on the Vehicle Emission Control Information label.
- Excessive knock sensor system spark retard activity-Refer to DTC P0324, P0325, P0326, P0327, P0328, P0330, P0332, or P0333 .
- Electromagnetic interference on the reference circuit, which can cause a misfire condition. You can usually detect electromagnetic interference with a scan tool by monitoring the engine speed parameter. A sudden increase in the engine speed parameter with little change in actual engine speed indicates that electromagnetic interference is present. Inspect the high voltage components near the ignition control circuit if a condition exists.
- Incorrectly operating crankcase ventilation valve-Refer to Crankcase Ventilation System Inspection/Diagnosis .
- Stuck open evaporative emission canister purge solenoid
Inspect the engine cooling system for the following conditions:
- A thermostat with incorrect heat range. Refer to Thermostat Diagnosis .
- Incorrect engine coolant level-Refer to Cooling System Draining and Filling (LSA, LS3, LS7, L99 Static Fill)Cooling System Draining and Filling (GE 47716) .
  For additional information, refer to Symptoms - Engine Cooling .
Inspect the exhaust system components for the following:
- Physical damage or possible internal failure.
- Restricted three-way catalytic converters.
  For additional information, refer to Symptoms - Engine Exhaust .
Inspect the engine for the following mechanical conditions:
- Excessive oil in the combustion chamber or leaking valve seals
- Oil consumption
- Incorrect cylinder compression
- Sticking or leaking valves
- Worn camshaft lobes
- Incorrect valve timing
- Worn rocker arms
- Broken valve springs
- Excessive carbon buildup in the combustion chambers-Clean the chambers with Top Engine Cleaner, if necessary. Follow the instructions on the can.
- Incorrect engine parts
  For additional information, refer to Symptoms - Engine Mechanical .
If the above conditions do not address the symptom, refer to the additional symptoms tests.