02 540i - CEL Flashing and car stutters

[Bimmerrules]

Every time I have to give a decent amount of gas to pass or merge the car stutter or misfires and the check engine light comes on blinking. It happened a few times and the CEL would stay on for a while and later go off.
Yesterday it happened again but this time the CEL stayed on and every time I hit the gas pedal the CEL starts flashing. I called my mechanic and he said "You must have dropped a coil". What does that mean? What is this related to? Does anyone have any idea how much this is going to cost? I just replaced the alternator not even a week ago and now this started happening just a few days later. Are they related at all? Is my mechanic ripping me off? HELP!! Thanks in advance!

[BimmerE39]

Dropping a coil means that one of your ignition coils or the coil pack is no longer functioning. This means that a spark plug attached to this particular coil is not firing which could potentially be causing a misfire. This could be determined by looking at the fault codes. The OBC will identify which cylinder is misfiring.

I don't believe the alternator has anything to do with the ignition coils. Depending on the amount of miles on your 540i, the ignition coils are likely worn out and might need replacing. If the ignition coils are in fact the issue rest assured it's a simple fix and you can even do it yourself easily.