Random Misfire

The scan tool indicates Diagnostic Trouble Code (DTC) P0300: Random misfire.




Troubleshooting
By test-driving, determine the conditions during which misfire occurs. Depending on these conditions, test in the order described in the table.

NOTE: If misfire doesn't recur, some possible causes are fuel that doesn't meet owner's manual specification, lack of fuel, carbon deposits on spark plug, etc.

Description
Misfire detection is accomplished by monitoring the crankshaft speed with the crankshaft position (CKP) sensor which is attached to the crankshaft.
If misfiring strong enough to damage the catalyst is detected, the MIL will blink during the time of its occurrence, and DTC P0300 will be stored. Then, after misfire has ceased, the MIL will come on.
If misfiring that increases emissions is detected during two consecutive driving cycles, the MIL will come on, and DTC P0300 will be stored.

NOTE: If some of the DTCs listed below are stored at the same time as a misfire DTC, troubleshoot those DTCs first, then troubleshoot the misfire DTC.

P1128, P1129: MAP sensor
P0171, P0172: Fuel metering
P0401, P1491, P1498: EGR system
P0505: Idle Control System
P1253: VTEC System
P1361, P1362, P1366, P1367: TDC1/TDC2 sensor
P1519: IAC valve

Possible Cause
- Fuel pump insufficient fuel pressure, amount of flow
- Fuel line clogging, blockage, leakage
- Fuel filter clogging
- Fuel pressure regulator stuck open
- EGR system malfunction
- Distributor malfunction
- Ignition coil wire open, leakage
- Ignition control module malfunction
- Valves carbon deposit
- Compression low
- VTEC system malfunction
- Fuel does not meet Owner's Manual spec., lack of fuel