Misfires on cold start

[Gumbercules]

Started up my car this morning and had 50 misfires before shutting it off. Started it again about 10 seconds later and had about 16. Shut it off and started again with no misfires and ran fine while driving (2-3 misfires while driving but I normally chalk that up to the tune sensitivity). There is no engine code accompanied by the misfires though, which I thought was kind of weird.

Car has about 65k miles on it and this is the first time I've had an issue like this pop up. I figured it might be the plugs as they're about 30k miles old, but I was wondering if there might be other issues that could cause such a large amount of misfires on cold start?

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[Cobra Jet]

Started up my car this morning and had 50 misfires before shutting it off. Started it again about 10 seconds later and had about 16. Shut it off and started again with no misfires and ran fine while driving (2-3 misfires while driving but I normally chalk that up to the tune sensitivity). There is no engine code accompanied by the misfires though, which I thought was kind of weird.

Car has about 65k miles on it and this is the first time I've had an issue like this pop up. I figured it might be the plugs as they're about 30k miles old, but I was wondering if there might be other issues that could cause such a large amount of misfires on cold start?

This thread may give some enlightenment to Ford's misfire strategies:
https://www.mustang6g.com/forums/threads/good-tech-article-on-ford’s-misfire-strategy.108076/

Also to note, this thread contains shop manual info about diagnosing the S550 misfires:
https://www.mustang6g.com/forums/threads/misfiring-even-after-replacing-coils.153240/#post-3124335

 

[Gumbercules]

This thread may give some enlightenment to Ford's misfire strategies:
https://www.mustang6g.com/forums/threads/good-tech-article-on-ford’s-misfire-strategy.108076/

Also to note, this thread contains shop manual info about diagnosing the S550 misfires:
https://www.mustang6g.com/forums/threads/misfiring-even-after-replacing-coils.153240/#post-3124335

Thanks, that was pretty helpful. Thought I was in the clear, but it happened again on Sunday and then again this afternoon. I was able to pull the Mode $06 data and it looks like the majority of the misfires are on Cylinder 1. I'll check the plugs this weekend and see if those might be the issue. If it persists after swapping them I'll bring it to Ford to check. Hopefully they don't blame the tune/mods I've got on the car.

 

[Jackson1320]

You already know what Ford will say. After plugs I would change the tune to stock if that’s possible and see if it is still missing

 

[Cobra Jet]

Thanks, that was pretty helpful. Thought I was in the clear, but it happened again on Sunday and then again this afternoon. I was able to pull the Mode $06 data and it looks like the majority of the misfires are on Cylinder 1. I'll check the plugs this weekend and see if those might be the issue. If it persists after swapping them I'll bring it to Ford to check. Hopefully they don't blame the tune/mods I've got on the car.

Swap the coil from #1 over to the adjacent cyl and see if the misfire now occurs on the adjacent cyl. If it does, it's a bad coil.

 

[Gumbercules]

Swap the coil from #1 over to the adjacent cyl and see if the misfire now occurs on the adjacent cyl. If it does, it's a bad coil.

Did this and was still getting misfires on 1. Swapped out the plugs tonight and noticed a bit of the ground electrode was worn away increasing the gap size. There was also quite a bit of oil on the threads, causing some excess fouling. Going to bring it into Ford to see what's going on with the oil buildup. Appreciate the help on this.

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