DTC Troubleshooting: P0300 (7x-1) and P0301 (71-1), P0302 (72-1), P0303 (73-1), P0304 (74-1)

DTC P0300 (7x-1):  Random misfire and any Combination of the Following:
DTC P0301 (71-1):  No. 1 Cylinder Misfire
DTC P0302 (72-1):  No. 2 Cylinder Misfire
DTC P0303 (73-1):  No. 3 Cylinder Misfire
DTC P0304 (74-1):  No. 4 Cylinder Misfire

NOTE:
  • If the misfiring is frequent enough to trigger detection of increased emissions during two consecutive driving cycles, the MIL will come on, and DTC P0300 (and some combination of P0301 through P0304) will be stored.
  • If the misfiring is frequent enough to damage the catalyst, the MIL will blink whenever the misfiring occurs, and DTC P0300 (and some combination of P0301 through P0304) will be stored. When the misfiring stops, the MIL will remain on.

1.Troubleshoot the following DTCs first if any of them were stored along with the random misfire DTC(s):
P0107, P0108: Manifold Absolute Pressure (MAP) sensor
P0131, P0132: Primary Heated Oxygen Sensor (primary HO2S) (Sensor 1)
P0171, P0172: Fuel system
P0335, P0336: Crankshaft Position (CKP) sensor
P1253: VTEC system
P1361, P1362: Top Dead Center (TDC) sensor
P1519: Idle Air Control (IAC) valve

2.Test-drive the vehicle to verify the symptom.

3.Find the symptom in the chart below, and do the related procedures in the order listed until you find the cause.

Symptom Procedure(s) Also check for: 
Random misfire only at low engine speed and under load Check fuel pressure. 
  • Low compression
  • Contaminated fuel
  • Manifold vacuum problem
 
Random misfire only during acceleration Check fuel pressure. Malfunction in the VTEC system  
Random misfire at high engine speed, under load, or under random conditions Check fuel pressure. Correct valve clearance