Miss on cold startup

[blue15gt]

I have a 2015 GT and recently it started missing when I start it up in the morning, after work, after sitting 4 hours or more.
It's only coming from the passenger side. Along with the miss there is an occasional metallic rattling coming from the passenger side of the engine when it's missing .
Kind of seems like maybe an oil type of issue since it clears up in 1 to 3 minutes and I can hear the miss get softer until it's gone.

Any ideas or suggestions?
Thanks

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[Cobra Jet]

Are you getting any stored codes?

What’s the oil level?

 

[sk47]

Hello; Let me say right off I am not up to date on the newer Mustangs so this is a very wild guess. I have a fuel injected car and have noted something similar to what you describe. Say I start the engine and only let it run briefly, then shut it off. When I start it later I will often have a miss fire type of rough running, like at least a cylinder is missing. It always clears up soon and then runs as normal.
I have been guessing the engine is still in the start up mode and maybe is still a bit rich in the fuel mix. Maybe fouling a plug which take a little bit to clear. I have learned to let the engine run till the RPM's drop if I only need to move it a short distance.

It could be you have an injector leaking down. Do a code scan as already suggested. Also you can do a leak down test if your fuel injection rail has a test valve. It will require a test gauge. This is only a wild guess.
Good luck

 

[blue15gt]

Oil lever is right where it should be. Haven't gotten a chance to scan yet.

 

[DeepImpact89]

Ever figure this out?

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