+1 I was going to recommend that his IACV aswell, seems like it is the only problem.. Just take it off and shake to listen and hear if the valve inside is loose. If not than thats your problem, because if it was too loose than it would be the problem but you'd be idling high, but it's the opposite so i'm guessing that your IACV is clogged and it'll be cheaper than you having an accident.