Sorry to hi-jack the thread but I'm experiencing the same problem and I'm frustrated beyond means because this is my daily driver and I can't afford to bring it to the shop. Same code: P0302.
Started last Thursday, noticed the car is idling rough and the CEL will blink intermittently when driving.
I bought a coil pack and a set of spark plugs (Bosch <-- dumb mistake) and swap one of my coil pack (the one closest to the passenger seat) and all four spark plugs. Car runs better, no CEL and no idling rough. Smooth rev.
This lasted for a couple days. CEL came on when car is idling on Sunday, same code but the idling is not as rough as last Thursday. Still smooth rev.
I then bought NGK spark plugs to replace the Bosch ones and I bought new wires and a new coil pack so that I'll have brand new wires, coil packs, and plug wires. Changed everything last night, turned on the car this morning and the idling is back to rough, CEL came on and it blinked intermittently again on the way to work. Engine rev is not smooth at all.
Any ideas on what I can do? I plan to work on it during lunch. There's also an Oreilly's auto store a mile away that I can drive to.