The faucet was working fine two weeks ago the problem started . I've changed H/C stems . If I run the H.2.O for a short time it sounds like air is being forced out and the problem is fixed for a short time and the problem starts allover

Close the angle valves under the sink remove both stems, open the angle valve one by one for a few second to flush out debris out the faucet, install the stems, now remove the Aerator from the spout see the image below clean and install try it now hope your problem is fixed, good luck.

John