Hello, I believe what the problem is, in your throttle switch or more often the connection to your battery, even though your battery might be good, bad or loose connection can cause this. Most electric toy cars, go carts, buggies, and other similar electric toys, all operated on a electrical switch mechanism. They are effective when working, but unfortunately from my experience poorly built, meaning they wear out real easy. When working properly, you press the pedal, activates the electrical circuit by way of the switch. Think of the switch as like the ignition on a automobile. It works kind of the same method.
I believe personally it is in your connection to your battery. However here is what did here to help you out. I have put to REAL GOOD links to help you. One link is to the sight, which shows you parts and cost for parts, and on same site i gave you the link that takes you to the Ground force trouble shooting guide of possible problem and solution based on the symptom. I think this will help you. Links are below and please copy and paste them in your browser and let me know if anything else i can help you with. Thanks Mike
Thanks Again, Mike , (Fiya Expert.)