I really hopes this helps others. About 3 months ago, my Blazer started missing, especially on damp days. The check engine read out usually indicated a maps sensor. From the rear bumper to the front, I replaced everything from the fuel pump to the plugs. Randomly, it kept missing. I would be driving, the vehicle would start stuttering so bad it would be concerning; then, run fine. The check engine light would turn on then off then on..... The stuttering felt like someone turning the gas on then off. As I was about to give up, I ran into the old mechanic at a parts store. He told me on Blazers, the gear connecting the distributor to the cam goes bad. I put in a whole new distributor sssembly $62 and it runs like new.