An omniscient god cannot be intelligent

[Angrboda]

That God is omniscient only makes intelligence unnecessary.  The problem comes in that reasoning to a conclusion is always less efficient than appealing to something already known.  Because God is perfect, he would never appeal to his ability to reason rather than his omniscience.  So his ability to reason is rendered unnecessary by his perfection, but that doesn't rule it out, either.  All we can say is that God doesn't employ his intelligence and is thus indistinguishable from an automaton which simply chooses the best available option based on his knowing what that option is at every moment.  This doesn't rule out an intelligent God, but it does mean that no natural theological argument can prove the Judeo-Christian God because intelligence is a requirement of that God, and no fact can demonstrate that any effect of God required intelligence (as I pointed out to Steve in The Absurdity Of God thread).  So it takes a whole lot of theist arguments off the board, including the Kalam cosmological argument, as well as Aquinas' five ways.

However, if a god was omniscient but unintelligent, how would you be able to tell he was unintelligent?

Well, that was my point. You wouldn't be able to do so. Thus the consequences for natural theological arguments.