We have a Price Pfister faucet in our kitchen sink and I just found this nice diagram of its layout in this PDF:

Usually, it operates by lifting the lever, which stays still in the up position until you turn it off. Recently, the lever would fall down slowly by itself, thus turning down the water. So one has to hold it up to keep the water running.

Now I reckon that the faulty part is the item 974-035 (some kind of cartridge which operate with some fluid I guess). I wonder if someone would confirm to me that this might be the cause of the problem (and not anything else related to water pressure, etc)? I think I might be able to get this part on-line.

I'd rather not buy a new faucet as the whole unit costs around $166.