zackcworley

So recently I’ve been having an issue with my car shooting a CEL every time I get to around 7,000 RPM in 3rd (6 speed) and I was wondering if anyone knew what could be causing it. It’ll start flashing then go away, then whenever I go to start the car the next time I drive it, the CEL will stay on until I clear it. The code read a P0300 Random Misfire, so I don’t really know what to do with that since it’s nothing specific. Just want some thoughts on what it might be.

houtex

Welcome to the forums!

So it occurs to me that the redline of a 2020 Mustang GT, in stock form of course, is 7000 RPM. So that you're getting up there is part of the issue, maybe don't? Of course, that's like telling me to not get Awesome up to her 6K redline, so I fully understand.

Since it's a random misfire, there's nowhere to send you except get a scan tool on it and then do the thing. You need one that can live data any misfires on all the cylinders. The Forscan tool should be able to do this, it's free as long as you have a Windows laptop and the dongle for it. I've not messed with it but I've got them if I need to figure out Awesome for something like this. Anyway, the 8 cylinders being monitored for misfires is what you're after, and then go make it happen, and not just once. When it happens, it may be just this particular cylinder, or it may randomly drop. You're hoping it's more of a particular cylinder, that you can attack.

Thing is it's under warranty (unless you modded it, or you've out-miled it) and so I'd schedule an appointment and say "Hey. It's not supposed to do this, fix it." Make sure YOU demonstrate the issue, not let them guess at how. If you're not under warranty, you're back to getting a scan tool yourself. Maybe a friend to help watch it.

And if it is randomly deciding to not fire a cylinder here and there, then you're generically checking wiring, plugs, coil packs, injectors, etc, ad nauseam... real goose chase. It may be the thing to do is to wait until a specific misfire happens, and a P0302 or such is thrown, then you could go after number 2. There's more to check, here's the page that generically shows what all it could potentially be.
https://www.obd-codes.com/p0300

Hope it helps. Good luck!

Bert

it sounds to me like you are hitting the rev limiter

I'm pretty sure the rev limiter works by cutting the ignition; and then the system sees this as a misfire . . . and I think it will clear itself after a while (not sure how long); assuming you don't hit the rev limiter again

try not hitting the red line so hard for a while, and see if it goes away

zackcworley

I appreciate the help, I’ll keep this thread updated if I figure anything out. I’ll get a scanner and watch the live data and see if I can figure it out with that.

shaneyusa

I would agree with @Bert on this one.

Ryunker

When you hammer down the pedal, the car goes into "open loop" and just dumps fuel. CEL flashes when too much fuel in the exhaust and the car can't control it. That along with the Rev limiter would explain this.