Rough Start after Sitting for A Week

Does changing the boots require buying new coil packs?

 

Cranks fine. Just idles rough for ~10 seconds and then is fine.

 

no, and they're cheap. I don't understand why they don't come with NGK wire packs.
They wear out just like a regular wire.

The popping is what makes them suspect to me.

 

Could be. It would run poorly until any coolant leaked into the cylinder burns off. How's your coolant level?

 

Happened again when I got back from vacation. Had a bit of a knocking sound for a couple seconds. Really hope this isn't the beginning of a bigger issue. Any additional ideas guys?

 

you've checked the injectors and replaced the boots?

 

I don't want to spread rumors but in I4 I had similar strange issue. Started in the morning idling rough like on 3 cylinders for maybe 5 - 10 seconds and then everything went away. Actually fuel consumption went down (I was doing 24mpg), but smog numbers were bad, very bad on NOx.

Cutting long story short I ended up with water leaking into cylinder via busted head gasket. Water in the cylinder made it not fire up for few seconds till all water was expelled. ECM compensating for "wet" cylinder was giving less fuel and that made my mpg and NOx numbers. After head gasket job smog numbers went to "like new", but the mpg wend down too to my normal 20mpg.