Ford Engine Misfire Or Rough Running Coil On Plug (COP) Ignition Systems

This article supersedes TSB 03-14-04 to update the vehicle applications and model years. ISSUE Approximately 50% of coil on plug (COP) coils returned for warranty do not have a problem. ACTION The misfiring cylinder must be identified through Self-Test misfire codes or through WDS Power Balance. Rule out base engine problems, rule out fuel problems, and then look at ignition problems (be sure to rule out coil primary circuit issues). Once the above steps have been completed, and the issue is in the secondary part of the ignition system, the oscilloscope procedure outlined in this TSB can isolate the difference between a coil or spark plug problem.

The following material will detail the diagnostic steps on WDS to take the guesswork out of misfire diagnosis using the COP Kit. The following procedure is for cylinder specific misfires and not random misfires. Random misfires have a different root cause and are not covered by this TSB. Misfire Definition: A misfiring cylinder is lacking power relative to the other cylinders. The causes for a cylinder specific misfire could be fuel, spark, or mechanical problems. Perform a thorough visual inspection. If no visible concerns are found use the following WDS tools for misfire diagnosis: • Self-test (Check for codes first) • Power Balance (Identify the cylinder of concern) • Relative Compression (Rule out a possible mechanical issue) • Fuel (Make sure fuel injectors are not restricted) • Ignition (Make sure spark plugs and coils are working properly) • Oscilloscope (Detailed signal analysis)

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