Code P0301 "misfire cylinder 1"

2020GT500 · Oct 5, 2022

So I started the car this morning to drop off for an oil change and got a CEL...?

Dropped car off 2 miles from home, oil changed, and dealer asked me to come back to further diagnose CEL, now a code P0301 - misfire cylinder 1.

I'm done for the season, time to store the car, and I wasn't leaving at the dealer overnight, so its home for now...

Searching the forum gives me little comfort that this is "just" a misfire due to a bad plug or coil...

Like most Google searches, its the worst case scenario that seems to be show up first.

Anyone out there have a "good news" story on a misfire?

Inthehighdesert · Oct 5, 2022

I did on my 350 when it was on the dyno for the whipple. One of the wires actually had a break in it from the factory. It just hadn‘t manifested itself until I started mess’n with the harness during the install. Hope its a simple fix.

kilobravo · Oct 6, 2022

Hey Andy, good to see you and I will echo the other sentiments, I hope it's No Big Deal.

tdstuart · Oct 6, 2022

Mom's BMW had some pretty bad misfires. Was just some bad coils.

Misfire can be a ton of problems. Spark plug, coil pack, wiring, fuel injector, damaged piston, damaged piston ring, damaged valve, bad ecu, and probably a few other things.

Realistically your engine probably didn't decide to fail overnight, and its probably a bad coil.

It's pretty easy to swap coils and swap spark plugs. Cylinder 1 should be really easy to get to (atleast on the 5.0, don't know how the supercharger impacts your access). I would swap the cylinder 1 spark plug and coil packs with cylinder 5's. Then take the car out for a drive. Reset the check engine light if you can, or alternatively leave the battery unplugged for a while. If the check engine light stays off then its next years problem. If it stays on go to auto zone and see if it code says the misfire moved, if it did then it is a bad coil or plug. If it didn't than it may be a more serious issue.

UncleSams_SVT · Oct 7, 2022

Not on a Shelby, but wife's ecoboost expedition's misfire was fixed with a new coil-pack and boot. But it could also just be a spark plug.

Worse case it is a wiring issue :surprised: