2019 Mustang GT misfiring on cold start

[Dave2017GT]

I'm not sure its misfiring but that's the best way to describe it. When i start the car it fires up just fine but then its little pauses as the car is warming up. I have been kinda brushing it off as no big deal but today i started her up and when i was backing out of the garage the car jerked during one of these misfires. It seems to be getting worse. Any idea what this is? Can't stand our Ford dealers in Florida because none of them give a crap about anything. More likely to scuff up my doors or scratch my leather than fix any problems.

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[Zathras]

Someone else posted something similar a few days ago. Sometimes when I start my '18, I think I hear tiny "gaps" in the rhythm of engine noise as if it missed a beat, but it's so brief it doesn't really affect the idle speed or make any noticeable vibration. Don't know about the jerk you mentioned, though.

 

[Elp_jc]

It's perfectly normal for cold engines to vibrate when cold, which is due to misfires; that's why you don't get a CEL. If you do, then you may have an issue. Fuel quality can exacerbate that. Bottom line is if there's no CEL, your engine is operating normally.

 

[Thegipper]

Someone else posted something similar a few days ago. Sometimes when I start my '18, I think I hear tiny "gaps" in the rhythm of engine noise as if it missed a beat, but it's so brief it doesn't really affect the idle speed or make any noticeable vibration. Don't know about the jerk you mentioned, though.

It may have been me who posted. When cold, after about 20 seconds (I finally timed it) it will stutter or skip a beat, sometimes it will do it twice in the first 30 seconds. It seems like it's common and even normal.

 

[W.O.T. Stang]

If its not setting a check engine light - i would not even give it a second thought.
There are a whole mess of programming parameters for every vehicle today for cold start (to heat the cats as quick as possible to reduce emissions). Keep in mind on the 18-19s, the spark and timing are greatly advanced, the high pressure fuel pump runs on the first 20-30 seconds of cold start up, fuel mixture is rich, and the charge motion actuators are being tested/activated. Its what gives 'cold start' exhaust clips that cold start sound. You are going to hear a lot more popping and grumbling - especially if you are modded, than what you are used too. Mine is stock with a resonator delete and i hear and feel the same thing if that makes you feel any better.

 

[Cobra Jet]

@Dave2017GT

See if anything in this thread sounds like your concern:
https://www.mustang6g.com/forums/threads/2016-mustang-gt-idle-dip-and-stall.114262/#post-2493417

 

[Chris Barnes]

My 2018 GT did the exact same thing. It would fire up just fine, then go into a skipping, pausing sound and oscillate RMP for about 5-10 seconds. It then returned to normal high warm up idle and was fine after. Mine was fine and normal up until about 8,000 miles then started doing it randomly out of the blue. It quickly got the point where it did it every cold start. Never had the issue with warm start. I emailed Lund and they messed with it a bunch and eventually tuned it out by commanding more timing I believe. Dakota told me their 2018 Whipple car does the identical thing. Very frustrating for sure since I spent weeks chasing down potential vacuum leaks, EVAP issues, etc. I eventually did a smoke test to verify there weren't any leaks.

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