Low Knocking Under Hood

'01 Accord. 68,000 miles. Automatic. 2 wheel dr. Making a slight knocking or ticking noise under the hood. It doesnt always occur, but when it does, its when I'm at a stop sign/traffic signal. Basically whenever the car is in drive but my foot is on brake. It is sometimes accompanied by a breif series of sputters, as if the vehicle is about to turn off. When the light turns green and I accelerate, the ticking stops; it will also stop if I put it in nuetral. Its very strange but it doesnt always happen. Any ideas?