Our single-handle Delta kitchen faucet was leaking slightly from the handle when it was turned on. I replaced the seats and springs using a kit from Ace Hardware. The leak stopped and the faucet worked great for a couple of weeks. Now, when we turn it on, either hot or cold, the pressure drops to around 10~20% of normal flow within about 2 or 3 seconds. If we turn it off and then back on, the flow is normal and then drops again within 2 ~3 seconds.By the way, we have very good city well water that is treated by reverse osmosis. There is no sediment problem. Our home is only 8 years old and our water pressure is great (90 psi +)

Remove faucet aerator, turn on faucet briefly. If pressure stay normal replace or clean aerator. If pressure continues to drop, remove spout and look for obstruction.

Ninety pounds of pressure is far to great. Adjust pressure regulating valve on main line into the house, if you have one. If not install one.