I was driving to work yesterday in the rain. It took me over an hour to get to work and was raining pretty hard. I was about five minutes away when all of a sudden my van starting running very rough and shuddered pretty bad when I accelerated. I limped it to work, borrowed a diagnostic reader from a colleague and found that I had misfire codes on cylinders 1, 5 and 6. My van has 105,000 miles on it. My first thought is that I should change the spark plugs which have about 45,000 miles on them but I don't understand why 3 would have failed at the same time. I also thought it might be an ignition coil, but also why would 3 fail at once. Any thoughts or advice would be appreciated.