This problem happened to me. It drove me nuts. The problem was with the connection between the spark plug cap and the coil wire. (usually the right side is the problem. Pull the wire out of the cap (it will not break it). Inside the cap you should see a clean brass colored prong that inserts into the coil wire. Mine was carroded (greenish). Soak for a bit in baking soda mixed with water and then scrape clean (carefully). Then flush it out with WD40. Check the other plug cap to see what it should look like. If that does not solve the problem then you will need to work on the inside of the spark plug cap (the part that connects to the spark plug). I found a way to do it on the internet and it worked. If you need info on how to do it I can send you the info and pictures of the fix. vancekerr@att.net