Cylinder 5 Misfire Still Present?

2007 LINCOLN MKZ
150,000 MILES • 3.5L • AUTOMATIC
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FREERIDER78
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Cylinder 5 misfires. I did a coil swap to determine it's still cylinder 5. When I did the injector pulse test on this cylinder the noid light flashed a few times and then stopped, indicating a problem with the injector circuit but not the injector. Could this be the ECM stopping the signal?
Jun 28, 2026 at 5:45 AM
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STRAILER
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Yep, it sure can, injector drivers go bad all the time inside the PCM. Fortunately I believe you can swap out the PCM without programming for this year, I would get a used one from eBay. Let me know how it goes.
Jun 28, 2026 at 10:47 AM
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FREERIDER78
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Would this be your chosen direction or are there more tests you would conduct?
Jun 29, 2026 at 4:26 AM
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STRAILER
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You may want to check the wiring and the condition of the pigtail @ the injector if they are okay the PCM is next. Here is a guide to help and the wiring diagrams so well.

https://www.2carpros.com/articles/how-to-check-wiring/

Check out the images (below). Please let me know what happens.
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Jun 29, 2026 at 7:12 AM
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FREERIDER78
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Replaced the PCM, programmed the key and the vehicle still exhibits the same issues. Codes, however, were not cleared. I don't think that would matter as wouldn't they be stored in the old PCM? I have to read new codes and check injector pulse with a noid light again. How would a bad connector or wire cut the pulse after three times?
Aug 6, 2026 at 8:20 PM
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STRAILER
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Did you do the testing with the injector connected when it looses pulse?
Aug 7, 2026 at 10:28 AM
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FREERIDER78
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No just the harness stopped sending pulse.
Aug 8, 2026 at 1:13 AM
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STRAILER
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Did you compare it tot he other injector leads to see if they do the same thing?
Aug 8, 2026 at 7:57 AM
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FREERIDER78
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They continue to send signals
Aug 8, 2026 at 9:29 PM
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STEVE W.
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Not unusual for the injector connectors to fail right at the crimp inside the plug for the injector. I've also seen the harness rub through and cause issues. I would check it over real close, look for any spots where it runs across corners or rubs.
Aug 8, 2026 at 11:13 PM
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FREERIDER78
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Ok I will do that and let you know what I find.
Aug 9, 2026 at 6:28 AM
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STRAILER
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Sounds good, have a good week.
Aug 10, 2026 at 10:50 AM
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