Symptoms Testing

Backfire, Cuts Out/Misses, Detonation/Spark Knock, Dieseling/Run-On, Hard Start, Hesitation/Sag/Stumble, Lack of Power/Sluggishness/Sponginess, Poor Fuel Economy, Rough, Unstable, or Incorrect Idle and Stalling, or Surges/Chuggles

1. 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 - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) .
     • Contaminated or a poor fuel quality condition-Refer to Alcohol/Contaminants-in-Fuel Diagnosis . Fuel that has deteriorated because of excessive storage time, or has inferior quality or octane rating can cause numerous driveability conditions.
   • 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 Base Engine Misfire with Coolant Consumption or Base Engine Misfire with Excessive Oil Consumption .
     • 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 (EI) System Diagnosis .
   • The operation of the automatic transmission. The incorrect engagement/disengagement of the torque converter clutch (TCC), the incorrect upshift/downshift of transmission speeds, excessive internal slipping, all can cause driveability conditions. Refer to Symptoms - Automatic Transmission .
   • The operation of the manual transmission clutch. The incorrect engagement/disengagement of clutch and incorrect clutch adjustment can cause driveability conditions. Refer to Symptoms - Manual Transmission .
   • The operation of the A/C compressor
   • Items that can cause an engine to run lean or rich-Refer to DTC P0171 or P0172 .
   • 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
     • Worn rocker arms
     • Broken valve springs
     • Excessive carbon buildup in the combustion chambers-Clean the chambers with top engine cleaner. Follow the product manufacturer's instructions.
     • Incorrect engine parts
   • Vacuum hoses for splits or kinks-Verify that the routing and connections are as shown on the Vehicle Emission Control Information label. Refer to Evaporative Emissions Hose Routing Diagram .
   • The correct operation of the knock sensor (KS) system. Excessive spark retard activity can cause a loss of power, poor fuel economy, and other driveability conditions. No KS requested spark retard can cause detonation. Refer to DTC P0325, P0326, P0327, or P0328 and Knock Sensor (KS) System Description .
   • The exhaust system components for the following:
     • Physical damage or possible internal failure
     • The three-way catalytic converters for a restriction-Refer to Restricted Exhaust .

       For additional information, refer to Symptoms - Engine Exhaust .

   • Electromagnetic interference (EMI) on the reference 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 circuit if a condition exists.
   • Inspect the positive crankcase ventilation (PCV) system and all connections for leaks or restrictions-Refer to Crankcase Ventilation System Inspection/Diagnosis .
   • Correct operation of the evaporative emission (EVAP) system-Refer to Evaporative Emission Control System Diagnosis .
   • 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 .
   • A camshaft position (CMP) actuator that is stuck in the advanced position-Refer to DTC P0011 or P0014 and Camshaft Actuator System Description .
2. If the above conditions do not address the symptom, refer to the additional symptoms tests.