C180 Auto Classic miss fire!
 

Hi, we nave a 1996 C180 Auto Classic, it has only done about 47k and treated with respect. Recently my husband noticed it had a slight miss fire, and as the parts for the leads and plug for genuine merc parts was astronomical, we bought them from else where. This seems to have slightly sorted the problem out. When the car is idle it only runs at about 500 and when you put your foot on the accelerator slightly to bring the revs up to about 750 it takes what we can only describe as the "shakes" away.
Does anyone understand what I am waffling about, if so any ideas?

Thanks;)

isn't the idle too low at 500 rpm in the first place?