Hi there, I was wondering if anyone stumbled upon something similar, either doing random modifications or a complete teardown. The car is a '05 Cooper S with 206,000 km.



Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

 

Looks to me like it’s not running on cylinder 1

 

It should show as misfires when you scan the car

 

That's the thing... it doesn't code when I'm driving it. It only coded twice lately and it's when I start the car to get it to the garage 30 feet away and start it shortly after, it will run on 3 cylinders and code for a P0301. If I clear the code and restart it, it's fine... For some time now I've been chasing something that feels like a misfire at highway cruising speed when the car is warmed up. When I go to work, it will sometimes start cutting out badly after like 10 minute if I'm going at a steady 130 km/h. No codes, no flashing CEL, nada. If I floor it, it's fine, no cutting.

The engine is currently out of the car to do the clutch and various gaskets (easier for me to pull the engine/trans out of the car at home with my engine crane rather than messing with the subframe). The intake side looks the same on all 4 cylinders, cam looks fine, no broken rocker arms from what I've seen. Ignition side is all new from me doing maintenance at 200,000. Oem coil pack and wires with 1 step colder NGK plugs (for the same mods I've had on the car for almost 9 years now, minus a new RMW header replacing the OBX one). Fuel filter was replaced last year as well.

At this point, I suspect either the injector on that cylinder (JCW 380CC installed in 2011) or something mechanical that I can't see without pulling the head...

 

Easiest for now would be to swap to injector of cilinder one and see if that shifts the issue. Might also be worthwhile to check the cabling going to the injectors?

[edit]
You might also keep the intake manifold off and turn the crankshaft pulley by hand to inspect what the intake valves do