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Home >> Chevrolet >> 2001 >> Camaro Base, 2D Convertible, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Engine Control System Self-Diagnostics - 3.8L) >> Diagnostic Tests >> DTC P0300-P0306: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Start and idle the engine. Review and record the scan tool Freeze Frame data. Operate the vehicle within the conditions present when the DTC was set. Monitor the scan tool Misfire Current Cyl # display for each cylinder. Is Misfire Current # display incrementing for any cylinder, indicating that a misfire is currently occurring? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. View the Misfire History Cyl # display with a scan tool. Does Misfire History Cyl # display a very large value for more than 1 cylinder? If yes, go to next step. If no, go to step  13.
  5. Inspect the vacuum hoses for splits, for kinks, and for improper connections. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  6. Inspect the crankcase ventilation valve for improper installation and for damaged O-rings. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  7. Inspect the throttle body inlet screen for damage or for the presence of foreign objects that may alter the air flow sample through the MAF sensor. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  8. Test the fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  9. Test the fuel for excessive water, for alcohol, or for other contaminants. If a condition was found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  10. Inspect the PCM injector grounds, the power grounds, and the sensor grounds to ensure that they are clean, tight, and in their proper locations. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  11. Inspect the following components for vacuum leaks:
    • The intake manifold.
    • The EGR adapter.
    • The EGR valve.
    • The EGR feed pipes.
    • The injector O-rings.

    If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.

  12. Remove the EGR valve. Inspect the valve in order to ensure that the pintle is not sticking partially open. Inspect the EGR valve pintle and seat for carbon deposits or for burrs that may interfere with the pintle closing completely. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  13. Test for proper fuel injector operation. Perform fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  14. Inspect the ignition wires associated with the cylinders that were misfiring. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  15. Install a Spark Tester (J 26792) at the spark plug end of the ignition wire for the cylinder that is indicated by the Misfire Current Cyl # counters or by the Misfire History Cyl # counters as having the most severe misfire, indicated by the largest number of counts. Jumper the spark plug end of the companion cylinder ignition wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil, for example, 1/4; 2/5; 3/6. Crank the engine while observing the spark tester. A spark should be observed. Is spark present? If yes, go to step  20. If no, go to next step.
    16. NOTE: If carbon tracking or terminal discoloration is apparent at the ignition coil end of any of the ignition wires, replace the affected ignition wire and the associated ignition coil.
  16. Remove and inspect the ignition wires associated with the cylinders that were indicated as misfiring. Ensure that the wires and boots are free of carbon tracking, and check the insulation for damage. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  17. Measure the resistance of the spark plug wires associated with the cylinders that were indicated as misfiring. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  18. Remove and inspect the ignition coils associated with the cylinders that were indicated as misfiring. Ensure that the coils and the coil towers are free of cracks and carbon tracking. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  19. Measure the ignition coil secondary resistance. If resistance is not 5000-8000 ohms, replace the malfunctioning ignition coils as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  20. Remove the spark plugs from the cylinders that were indicated as misfiring. Inspect the spark plug electrodes for excessive fouling. Was a problem found? If yes, repair engine mechanical problem. See appropriate article in ENGINES. If no, go to next step.
  21. Inspect the spark plug insulators for cracks, for carbon tracking, or for other damage. Inspect spark plug electrodes for incorrect gap. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  22. Inspect for an engine mechanical condition. See appropriate article in ENGINES. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  23. Inspect for a transaxle Torque Converter Clutch (TCC) condition. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a condition is found, repair the transaxle as necessary. Did you find and correct the condition? If yes, go to step  25. If no, see DIAGNOSTIC AIDS .
  24. Replace the ICM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  25. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  26. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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