I got 2004 VW Passat 1.8L turbo with 70K miles. About week ago there was a misfire in the engine, so i changed all 4 spark plugs and changed all 4 egnition coils. It was working normal again, then I drove about 100 more miles and now same problem happened. It showed misfire in cycinder 4, i tried to swtich coils back and forth and now it shows Random engine misfire. Hmmm does not look like it just coils? What can the problem be? what what causes this promlem. Thank you.