[taranfx]

I ordered N55 spark plugs & ingition coils from FCP Euro. Disconnected battery, replaced spark plugs & ignition coils with new ones now cylinder 4 misfires (P0304 Cylinder 4 misfire detected). I didn't use any dielectric/grease. I made sure its torqued at 17 lb-ft with a husky torque wrench.

In order to diagnose, I removed the spark plug & ignition coil in 4th cylinder and replaced with cylinder 1. Now 1 misifres. Replaced cylinder 1 with original coil/spark plug. No misfire so far but I hear minor hesitation & very minor occasional shake when idling.

My car is all stock.
What should I do?

N55 2011 135i