How do you fix Moen 7590 single faucet How do you remove cartridge from Moen faucet?

I just replaced mine. I would recommend buying the Moen original valve, #1225. I paid $20 at HomeDepot.

The factory valve has a tool that help you remove the valve. The tool is a plastic cap that fits on top of the valve and lets you rotate it back an forth to loosen it.

The trick is that you need to remove the retainer clip (1883) first. Remember the order of the parts. It can be tricky.

Make sure the hot and cold are correct. Just take the handle off again and rotate the valve.

See the link below for a drawing of the assembly from Moen.

Stevegto; I want to thank you for your helpful answer. It took me 20 minutes to replace the cartridge. My problem was the valve would not turn off upon pressing down on the handle. To turn off the faucet you had to press down on the center of the unit and not use the handle. Replacing this worked great. I did find locating the retaining clip was a challenge as it was the same color as the unit itself. Once I removed that, the unit came out easily. OF course the plastic cap included did help me move the cartridge back and forth as you mentioned.