check your blue plate. The actual pickups on it... Here is what happens: when you install the blue plate, most people just throw it on, adjust the timing, and tighten the screws. This will work for a while, but most likely you will have problems down the road. The reason is that there is that you need to set the clearences between the rotor on the crankshaft, and the actual pickups (the black pieces on the blue plate) When you install the blue plate, take 2 matchbooks, and fit the thickness of the matchbook cover in between each pickup and the rotor. (a 13-14 thousandths feeler guage works too, but I have found that a matchbook is easier.
To check if this is the problem, remove the pickup plate and look at the inside surface of the pickups. if there is any worn, or flat spots, they are likely the problem. What happens is with to little clearance, over time, all the dirt, rubber, etc, that gets thrown up, rubs away at the pickups. This could take a month, or it could take 3 years, but it will happen if there is not enough clearance, and it will drive you CRAZY trying to find the problem. I have found the problem also gets worse as the engine warms up, not sure why, but it seems to me it does.
