Symptoms Testing

Test for the following conditions:
- The fuel system for the following:
  - Correct fuel pressure - Refer to Fuel System Diagnosis .
  - Fuel injectors that are leaking or improper operation - Refer to Fuel Injector Solenoid Coil Test .
  - Contaminated or a poor fuel quality condition - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- The ignition system for the following:
  - Spark plugs for incorrect heat range or an abnormal condition - Refer to Spark Plug Inspection .
  - For diagnosis of coolant or oil fouled spark plugs - Refer to Loss of Coolant or OIL CONSUMPTION DIAGNOSIS .
  - Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may 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 .
- The operation of the transmission torque converter clutch (TCC) - The scan tool should indicate an engine speed drop when the TCC is commanded ON.
- The operation of the A/C compressor
- Items that can cause an engine to run lean or rich - Refer to DTC P2177, P2179, P2187, or P2189 .
- The crankshaft position (CKP) sensor for an intermittent condition-Observe the scan tool CKP Resync parameter. The Resync parameter should remain at 0 during all operating conditions, and when moving the related harnesses and connectors between the CKP sensor and the ECM.
- The engine for the following mechanical failures - Refer to SYMPTOMS - ENGINE MECHANICAL .
  - Excessive oil in the combustion chamber or leaking valve seals
  - Incorrect cylinder compression
  - Sticking or leaking valves
  - Worn camshaft lobes
  - Incorrect valve timing
  - Broken valve springs
  - Excessive carbon buildup in the combustion chambers - Clean the chambers with top engine cleaner. Follow the instructions on the can.
  - Incorrect engine parts
- Vacuum hoses for splits or kinks
- Knock sensor (KS) system for excessive spark retard activity - Observe the Knock Retard parameter for activity greater than 0°.
- The exhaust system components for the following:
  - Physical damage or possible internal failure
  - The three-way catalytic converters for a restriction
    For more information, refer to Symptoms - Engine Exhaust .
- Electromagnetic interference (EMI) on an ignition control circuit can cause a misfire condition. You can usually detect EMI 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 EMI is present. Inspect the high voltage components near the ignition control circuits if a condition exists.
- Inspect the positive crankcase ventilation (PCV) system and all connections for leaks or restrictions.
- Evaporative emission (EVAP) canister purge solenoid that is stuck open
- The engine cooling system for the following conditions:
  - The thermostat is the correct heat range - Refer to Thermostat Diagnosis .
  - Proper engine coolant level - Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (Vac N Fill) .
If the above conditions do not address the symptom, refer to the Additional Symptoms Tests .