I have a 2004 Chevy S-10. Every time I go up long hills (1 mile) the engine starts to miss and the check engine flashes. When I get to the top, the light quites flashing and the engine goes back to running normally. There is no code that come up when I get it checked afterwards. The only code I have ever gotten was a #5 cylinder misfire before I changed the plugs and wires. The truck runs fine everwhere else.

Be sure to only use the same ACDelco spark plugs that originally came in the truck.