Vehicle: 2011 Ford E 450, V10-6.8L, Automatic Transmission
Problem: The engine in this van had been replaced by another shop and the MIL was on. They had replaced the spark plugs and installed new coils but the misfires continued.
Details: When the customer brought it to the new shop, the tech retrieved DTCs: P0300, P0301 and P0307. A static compression test revealed no mechanical problems.
With a scan tool connected, the tech checked the misfire counts and noticed that the misfire counts increased between 1500-2000 rpm in Park or Neutral and in 4th and 5th gear between 1500-2000 rpm. Under load, the misfire counts went to zero or were very minimal – the opposite of what you would expect.
Confirmed Repair: The technician performed a Misfire Monitor Neutral Profile Correction Relearn procedure and the problem was cured.
System Strategy: For the misfire detection system to function correctly, any mechanical inaccuracies in the crankshaft position (CKP) sensor must be learned by the PCM. Neutral profile correction learning should be accomplished using a scan tool any time the PCM, CKP sensor or the crankshaft pulse wheel is replaced, or when major engine repairs have been completed.
To determine if the neutral profile learning has been completed, check the MP_LRN parameter identification (PID) using the scan tool. The PID should read YES if the neutral profile learning has been completed. If the PID reads NO, complete the neutral profile learning prior to diagnosing any misfire DTCs.
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