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 Balance Test with Special Tool .
  - Contaminated or a poor fuel quality condition.
- The ignition system for the following:
  - Sparkplugs for incorrect heat range or an abnormal condition. Refer to Ignition System Specifications .
  - For diagnosis of coolant or oil fouled spark plugs, refer to Loss of Coolant in Engine Cooling or Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91).
  - Weak spark using the J 26792 Spark Tester. Refer to Electronic Ignition (EI) 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. Refer to Symptoms - Automatic Transmission in Automatic 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 crankshaft position (CKP) sensor for the correct resistance. The CKP sensor resistance may be out of range after a hot soak. The resistance should be between 460-620 ohms.
- 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 instructions on the can.
  - 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 Emission Hose Routing Diagram.
- Knock sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description and DTC P0327 .
- 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 in 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.
- The crankcase ventilation valve for leakage or restriction..
- 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 in Engine Cooling.
  - Proper engine coolant level. Refer to Draining and Filling Cooling System in Engine Cooling.
If the above conditions do not address the symptom, refer to the additional symptoms tests.