TGOH

So, yesterday I played a round at Cherry Island, a relatively nice course in the Sacramento area. I played pretty well, by my standards, and shot an 88. This was only the second time I've broken 90, so, naturally, I'm happy with that.

What I noticed was that I was striking the ball well with my irons. It seemed like anything I pulled out of my bag I hit well...Except my 4 iron. I used it once, and sliced a weak shot in to the water, and ended up doubling the hole. This wasn't a rarity either. I only had to use it once yesterday, but that weak slice is a common occurance whenever I pull it out of the bag.

What gets me is that this is the only club I hit poorly consistently. Any suggestions as to why this might be and how I could remedy it?

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Driver: Taylormade R7 Draw 10.5*, R flex, Re Ax 55 gram tip soft shaft.
3 wood: Tommy armour 845FS Silver Scot 15*
3 hybrid: Taylormade Rescue Mid 19*
Irons: 4-PW Taylormade R7
GW/SW: Taylormade RAC 50*/56*
LW: Nike Forged 60*
Putter: Ping Zing 2, 34", Green dot