2004 Ford F-150 4.6L MIL Lamp on Injector Circuit

Car problem question:

This 2004 F150 4.6L has an ignition coil fault code which causes the engine to misfire on # 2 cylinder after 1-2 minutes of running. Normal ignition tests were done: relocated injector #2 to injector #3; compared noid light brightness on all injector terminals, removed and open up harness wires between PCM injector pin terminals up to the injector coil wiring terminals to check for continuity, power and ground...all of these tested OK. We did to verify if the there is a short on those wires and none found. Finally, a good known PCM was installed and same results. What have we missed?

ATS Adviser:

How about the mechanical condition of # 2 cylinder itself? If the cylinder developed a misfire during initial runs then the PCM will cut off the supply of fuel to that cylinder to protect the catalytic converter from being damaged. Once you determined that after swapping injectors and the missed stayed in # 2 cylinder, testing the cylinder mechanical condition should be the next inspection instead of testing the wiring harness which takes time to do.

FINAL FIX:

We wasted a lot of time doing unnecessary test on the injector circuit. I guess we learned from one's mistakes. After doing a cylinder leak down test, we found #2 exhaust valve was intermittently leaking. A new head job corrected the problem.

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