I get slow wiper motion too (along with wipers not wanting to shut off when cold).
I have a spare wiper motor, if anyone has "fixed" the wiper setup, I'd like to read about it.
I have a spare (from a 12,000 mile wreck!), but my ~400,000 mi factory motor is still going strong. The problem is the wiring harness contacts.
Wipers not shutting off (sometimes/always) is the removable contact spring switch thingamajig under the removable cover (it comes out with no tools, just a plastic tab). Most likely, it's corrosion on the wire harness contacts, not an issue with the spring switch itself.
To "FIX" my wiper setup, I ganked some JY switches and soldered wire leads directly to the 2 metal contacts on the switch, then used bullet connectors to hook it up to the body harness. I carry a spare switch that is setup like this as well as an unmodified switch (factory plug remains, disconnected). New factory connector pins/plug might be available, but I'm not sure. My rig was parked near ocean for years before I got it, so simple cleaning of the contacts wasn't good enough in my case.. I've slowly been replacing all my wiring.
As for slow or sometimes not working motor, that's usually corrosion on the other (3 wire) plug contacts. If your motor works at all, chances are very good it's mechanically sound and your wiring harness needs attention. Mine stopped working entirely on a wet day once, fiddled with plug to no avail, then they started working awesome a few miles later and have been awesome/fast ever since.
HTH.
