Speedometer erratic

1992 Plymouth Voyager1992 erratic speedometer not all the time and sometimes power slowdown when speedometer goes wild

It sounds like a faulty VSS (vehicle speed sensor) or perhaps the wiring to it is loose or chafed.

I mentioned this to my mechenic and maybe because I also sometimes get a power loss he thinks it is something else but I will run this too him again

This happened to me also. I have an 85 though but it ended up being the front shocks/struts. They were so worn that the wheels would hop over bumps coming off of the road and making the speedo move around like crazy. I put on new struts and the problem went away.