So the issue is:

ive got a check engine light that came on. I went and had the code read, it was a misfire in cylinder one, I changed the spark plugs and the CEL went away. After driving for around two weeks it came back on this time it was a misfire in clylinder 4, but if you messed with the spark plug wires the CEL would shut off. So I decided to purchase new wires and new spark plugs (yes the four pronged ones for the jcw) the CEL didn’t come back. I drove the car for 4 days after installing the new wires and plugs Now the CEL is back on with a misfire on clylinder 4 again. The coil pack itself has corrosion on the #3 prong, I just put a full tank of gas in the mini as well.

might I add ever time the CEL has come on the mini doesn’t drive/run any different, never bogs down, doesn’t feel like it’s lost any power and doesn’t idle funky. If it does run differently it for sure not enough to notice.

What in the world would cause this misfire to jump around then stay steady on one cylinder?

Coilpack? Fuel injector?

My my next step is to change out the coil pack since I’ve asked a few mechanics and they said it sounds like that’s the culprit but I’d like a few opinions.

Ive for sure seen the issue with the corrosion and seen it’s pretty normal for these coil packs to corrode on that specific prong. I wanted to make sure I included as much detail as possible so maybe it’s earier for someone to help me. I thought it was a faulty plug wire since if you wiggles them the CEL would go off but now it’s just steady one and won’t go off
I placed an order for the coil pack already should arrive next week.

it’s worth a shot checking! But if the senor was biting the dust wouldn’t it pop a code for that sensor? Granted I’m not using a bmw/Mini specific code reader, so I’ve got a generic read “ misfire on cylinder 4 detected”

I’m pretty sure owner 1 or 2 already changed it, I’ll double check the car fax.
Im owner 4 for this mini.

Owner 3 indicated when I purchased the vechile it was upkepy and has never had any issues at all.
owner 1,2 and 3 up kept this car with regular maintenance from the mini dealer, owner 3 took it to a mini specific garage.
Although im not sure if the “carbon buildup” has ever been cleaned, sensors changed, and I’m pretty sure coil pack has never been changed due to the corroded prong it has. so I’m going to assume that spark plugs as well as wires were also never changed. But I could be wrong on the spark plugs..

My next step is changing the coil pack itself and seeing if the CEL disappears

hm will have to check them out and see if theres any damage present.

Hopeing its the coil pack though simple fix
possibly it’s having a fit due to its age

I Tried fildeling with wires, as well as swapping the #4 with the old wire and checked to make sure all sensors(that I could see) were Connected, also follwed ignition wire to harness and inspected for damage to wires. Didn’t see anything odd or broken.

Everytime I shut the car off unplugged something plugged it in and turned it back on. Total shut offs were 5. I had to drive the mini to the grocery store (not too far maybe 7 miles round trip) pulled into the drive way shut off the car. Decided I wanted to try the infamous “dollar bill test” so I turned the car back on CEL was shut off. 🤨

maybe good news that I’m pretty sure the dollar bill test was passed didn’t notice one bit of sucking. That exhaust is indeed blowing steady and pretty hard if I lost grip of that bill it would have went flying.

on a side note are these temps normal? For oil pressure, oil temp and regular running temp? Photo was taken at idle

Changed coil pack yesterday, still have a CEL on for p0304 misfire on cylinder 4

next step is to do a compression test.

How do you go about doing so?
Obviously pull the “power” wire off the coil pack

But do you pull the fuel pump fuse?
do I need to hold the gas pedal down while turning engine over?

Ive seen roughly the psi league that I should be getting for each cylinder
I’ll be renting the tool from the local parts store

starting to think it’s a valve issue or still could be the camshaft senor

mini Cooper dealer hasn’t touched it yet but I called to get prices 140$ to diagnos it. And 7000$ to rebuild the head lol that’s more than what I paid for the car lol. I do t have the space to do a value job right now

But Lets assume it is a valve issue
do I need the entire head re done (which is not affordable at all) or just the valves changed?