Low water pressure in sink...(kitchen)?

My husband replaced the faucet on our kitchen sink. Since he has done this there has been no water pressure... I am going nuts. I have taken the whole exterior part of it (above the sink) to make sure all the screens and no nlokages etc... Nothing... Can anyone tell me how to fix this?? The faucet is one that has the handle attatched to the hose so you can pull it off the base... Help!!