Hello, I've been trying to get my Mini Cooper R56 running for the last 3 months after I rebuilt my engine. I have an N16 engine and everything on the engine is brand new expect for the crankshaft, I put in the next sized pistons above the stock size. I've checked spark, air, and fuel and all are good, but the engine continues to misfire on all cylinders the only codes I get are misfires. Whats strange is the car misfires a lot whens it dead cold but when it warms up it stops misfiring, but if I Rev the engine it will misfire on all cylinders. I've checked the timing three times using the ECS timing chain tool kit, and it looks good every time. The compression is 130psi on cylinder 1 and 2 and 135 on cylinders 3 and 4. My only idea now is that the fuel map in the ECU is incorrect for the larger bore. Any idea or pointers are highly appreciated.

 

I would be concerned after a total rebuild with bored cylinders and larger pistons that your compression is low. I would expect ~150 across all cylinders. It sounds as though you may have leakage. Did you have both the head and block decked?

 

Yes both the head and block were decked only a couple of thousandths since the machine shop said they were pretty flat already.

 

Also according to the mini cooper shop manuals the cylinder should be between 8-12bar(116psi-174psi)

 

I just did a cylinder leak down test to make sure nothing is leaking from the valves or pistons and in the process of doing that I heard a click come from the piston on cylinder 1 and cylinder 4 when i had it at 20 psi. Which makes me think the piston might be rocking back and forth. The click noise from the piston will only happen once, in order for it to happen again I have to rotate the piston up and down a little bit then the click will happen again. From my experience I think the rods wrist pin bearing might to too lose and letting the piston rock in the cylinder. In any case here are the leak down results if your curious.

Cylinder 1: 93psi/100psi
Cylinder 2: 98psi/100psi
Cylinder 3: 97psi/100psi
Cylinder 4: 92psi/100psi