DTC P0301 - Cylinder No. 1 Misfire; DTC P0302 - Cylinder No. 2 Misfire; DTC P0303 - Cylinder No. 3 Misfire; DTC P0304 - Cylinder No. 4 Misfire; DTC P0305 - Cylinder No. 5 Misfire; DTC P0306 - Cylinder No. 6 Misfire
- Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
- Start engine and run at idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within FAILURE RECORDS conditions. Read MISFIRE CUR # display for appropriate cylinder. If MISFIRE CUR # increases (indicating an occurring misfire) for affected cylinder, go to next step. If MISFIRE CUR # does not increase, check for an intermittent problem. See TESTS W/O CODES article.
- Monitor MISFIRE CUR # while operating vehicle and attempting to duplicate conditions which caused DTC to set. If MISFIRE CUR # increases, go to next step. If MISFIRE CUR # does not increase, check for an intermittent problem. See TESTS W/O CODES article.
- Check intake manifold, injector "O" rings, EGR valve and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
- Install spark tester at affected cylinder spark plug wire. Crank engine. If a strong Blue spark is present, go to step 8). If no spark or weak spark is present, go to next step.
- Remove ignition coil related to misfiring cylinder. Check ignition coil for cracks or carbon tracking. If a problem is found, replace damaged coil. Retest system. If no problem is found, go to next step.
- Using an ohmmeter, measure primary coil resistance. Resistance should be 0.8-1.3 ohms. Replace ignition coil if resistance is not as specified. If coil is okay, replace ignition control module. Retest system.
- Remove spark plug associated with misfiring cylinder. Check spark plug for excessive fouling. If spark plug is excessively fouled, diagnose and repair mechanical engine problem. If spark plug is not excessively fouled, go to next step.
- Check spark plug insulator for cracks, carbon tracking or other damage. If a problem is found, replace faulty spark plug. Retest system. If no problem is found, go to next step.
- Perform INJECTOR BALANCE TEST. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
- Inspect injector "O" rings for vacuum leaks. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
- Diagnose mechanical engine problems such as: faulty camshaft, leaking or sticking valves, weak valve springs, damaged piston rings, loose or worn rocker arms, incorrect valve timing, leaking head gasket or loose or broken motor mounts. If a problem is found, repair as necessary. Retest system. If no problems are found, check for an intermittent problem. See TESTS W/O CODES article.