My Vauxhall zafira 02 is making a thumping/clicking/banging noise coming from engine when I accelerate it's really loud its like its missing/workig to hard.so in order for me to get car home I took it easy keeping steady pace trying not to stop start as little as possible as then the noise wasnt as bad recently had the coil pack replaced but didn't replace plugs/sparks would this be a reason for it or am I just hoping and it's something more serious!! Please a little lady in need of a reliable car