I have always had low water pressure at upstairs shower, while good in rest of the house. After turning off water to repair toilet valves, I have just a trickle from that shower, (cold and hot) and a tricke of hot water with good cold at sink next to shower. My basement sink has also lost all water while the shower next to it remains good. I have removed valves at shower to clean. They showed no sign of lime-build up. Turned water on with valves out and water flowed great. Any thoughts on air in lines or what needs to be done would be greatly appreciated. I am on city water.
Thanks in advance!:)

Air in the lines would give you some big sputters which I am not hearing so lets move on. Did you remove the shower head and test the volume/press without the head? Shower heads lime up faster than valves. Did you remove the sink faucet aerator, try that and clean it.

I have removed both shower head and aerator the sink. The water trickles, at shower. When you plug it up with hand the water will build up but no pressure.

I have removed both shower head and aerator the sink. The water trickles, at shower. When you plug it up with hand the water will build up but no pressure.