knocking/coilpack
 

Hi all i was in traffic and heard what i thought was the dreaded knock. The car then missfired badly as i pulled over. I opened bonnet and it was knocking from heads. It turned out that the coilpack bolt had come loose and coilpack was hanging off. After refitting the knocking sound has gone. What could of caused the knock sound and will my engine have any damage now? It sounds and drives fine now. Thanks