Help? Cart is possessed

[returntoport]

I have a 1992 EZ Go Marathon 1000E Workhorse 36 volts. I bought the cart and it did not work. Here is what I have done, replaced the batteries, solenoid, diode, and new 4 guage battery cables on the batteries and the cart then did work. Periodically now it will not work and other times it will. I've downloaded the service manual and gone through the service check list to track down the issue with no luck. The solenoid clicks when you push the pedal but no go. I've checked voltage at the batteries 37.4 volts. I have the same voltage at the controller. I removed the wires at the motor and jumped the motor terminals and the motor runs. I replaced the ITS sensor. I still have the same problem of one time it works fine then the next won't run at all or when it does run I have low power. When I push the pedal the cart will take off but slowly looses speed and eventually slows down to nothing in a matter of 30 feet of travel. One day the cart works fine then the next it just won't go or does what I previously mentioned with little power and slows down to nothing. What should I do?