DTC P0300-0308: MULTIPLE CYLINDER MISFIRE Dodge Durango I

Note. For DTC and cylinder misfire identification, see CYLINDER MISFIRE IDENTIFICATION table.

Note. Cylinder misfire is monitored anytime engine running and adaptive numerator has been updated. DTC may be stored in Powertrain Control Module (PCM) when more than a 2 percent misfire rate is measured during 2 trips or with a 10-30 percent misfire rate during one trip. Possible causes are: defective camshaft or crankshaft position sensor, improper engine valve timing, vacuum leak, defective ignition system, engine mechanical problem, fuel contamination, carbon deposits on valves, weak valve springs, improper torque converter stall speed, improper fuel pressure or capacity, or defective fuel pump.

CYLINDER MISFIRE IDENTIFICATION

1. Turn ignition on with engine off. Using scan tool, check for DTCs. If MISFIRE GOOD TRIP counter is displayed and equal to zero, go to next step. If MISFIRE GOOD TRIP counter is not displayed and equal to zero, go to step 3 .
2. At this time, conditions required to set DTC exist. Using scan tool, read FREEZE FRAME data and SIMILAR CONDITIONS WINDOW data while operating vehicle in the similar conditions in which DTC was set. When in SIMILAR CONDITIONS WINDOW, go to WHICH CYLINDER IS MISFIRING monitor on scan tool. If scan tool is not counting misfires at this time, go to next step. If scan tool is counting misfires at this time, go to step 4 .
3. At this time, misfire does not exist or is an intermittent problem. Intermittent problem may be caused by moisture in the ignition system components. Using scan tool, read FREEZE FRAME data and SIMILAR CONDITIONS WINDOW data. Attempt to duplicate the condition that causes DTC to be set. While using FREEZE FRAME data, pay attention to the conditions such as vehicle speed, temperature, load and Manifold Absolute Pressure (MAP) sensor vacuum. Recheck for DTCs. If DTC for misfire exists, go to next step. If DTC for misfire does not exist, check for related Technical Service Bulletins (TSBs). Perform «TEST VER-7»(ref-9482-S39715858482000102700000) .
4. Using scan tool, read FREEZE FRAME data and attempt to determine the cause of misfire. In FREEZE FRAME data, note the adaptive fuel percentages. If adaptive fuel percentages are not more than 15 percent plus or minus, go to next step. If adaptive fuel percentages are more than 15 percent plus or minus, fuel pressure and fuel pump volume must be checked. See «TEST NTC-7: CHECKING FUEL DELIVERY»(ref-9482-S09958255042000102700000) .
5. Using scan tool, read LOAD VALUE under FREEZE FRAME data. If load value is 50 percent or less and engine coolant temperature is not within operating range, go to next step. If load value is more than 50 percent and engine coolant temperature is within normal operating range, check secondary ignition system, compression and cylinder leakage. Perform «TEST VER-7»(ref-9482-S39715858482000102700000) .
6. Using scan tool, read ENGINE RPM under FREEZE FRAME data. If engine RPM is 3000 RPM or less and engine coolant temperature is not within normal operating range, go to next step. If engine RPM is more than 3000 RPM and engine coolant temperature is within normal operating range, use lab scope to test camshaft and crankshaft position sensors, check engine valve timing and engine vacuum. Perform «TEST VER-7»(ref-9482-S39715858482000102700000) .
7. Check following items for possible causes of a cylinder misfire: Defective Fuel Injector Wiring Harness, Connectors Or Fuel Injectors Defective Ignition System Components Engine Mechanical Problem Defective PCM Power Or Ground Connections Irregular Cam Or Crank Signal Restricted Exhaust Or Air Intake System Defective Trigger Wheel Contaminated Fuel Vacuum Leak Weak Valve Springs Carbon Deposits On Valves
8. If any of the problems listed exist, repair as necessary. Perform «TEST VER-7»(ref-9482-S39715858482000102700000) . If none of the problems listed exist, check for related Technical Service Bulletins (TSBs) and go to next step.
9. Check for following additional items for possible mechanical problems which may cause a misfire. Improper engine vacuum (should be at least 13 In. Hg with transmission in neutral). Improper engine valve timing. Compression is not within specification. Restricted PCV. Improper torque converter stall speed. Internal vacuum leak in power brake booster. Restricted fuel injectors or improper fuel injector wiring.
10. If any of the causes listed exist, repair as necessary. Perform «TEST VER-7»(ref-9482-S39715858482000102700000) . If none of the causes listed exist, test is complete.