Need some help with my R55, got a misfire on cyl 1 i cant figure out.
Things i've checked/done todate.

1. coil packs, ohm'd out all the same, swapped around, no change.
2. new plugs, swapped around, no change
3. compression checked, similar on all 4
4. fuel injectors ohm'd, all the same, swapped around, no change
5. ecm codes cleared after each step.
6. data stream on cyl 1 misfire, worse at idle, goes away when rpm's reach 2500, runs smoother.

any ideas? i am at a loss.
thanks in advance

 

Did you ever find a solution? Sounds like my current r55 but mines on #4

 

Check your intake (and if turbo) boost system for leaks (including the boost bypass), check the PCV for leaks. unmetered air into the intake can cause misfires and if it's getting in somewhere near that part of the intake it could impact only one cylinder. and if you're a turbo once the intake gets pressurized the problem would go away as the leak is small compared to the air flow.

mechanics with smoke machines will smoke test it but you can also find ways to pressurize the entire intake to see if you can find leaks. (I did this with my Saab by blocking off certain pipes)