Bringing this problem alive again...I have this same problem EXACTLY. This is the only place I've found on the web with the same problem as me. I'm a little confused on why it would be the cap when it's temperature related? I have replaced cap (yes autozone brand), rotor, wires, AC Delco Plugs, coil, crank position sensor, fuel filter, TPS, cleaned my MAF too. I too have pulled the P0300 1 time, shop replaced crank shaft position sensor, but still have the same problems. I've even blasted it with Seafoam, no change. Here I am thinking it's the injectors or fuel pressure problem until I read this, but doesn't make sense. UNLESS it has to do with early morning moisture??? Maybe. I will replace my cap with AC Delco and report back. Hope this makes 2 of us with the same outcome of just a darn cap.