Rc Nitro wheels move when the car is in neutral. the clutch is fine please help ???

hi there i have a 1:10 nitro gas car. it has 18cxp vertex engine. When i start the car the wheel start to spin really fast in neutral, i can stop this by applying the brake. I have checked the clutch shoes and they are prefectly fine. I closed the throttle by adjusting the idle screw this how ever slowed down the wheels moving but the car started to hesitate and the noise changes as if the engine was going to shut off on me?? what other needled do i need to adjust in ordered to stop the wheel moving in neutral ??Rc Nitro wheels move when the car is in neutral. the clutch is fine please help ???Couldn't tell you how to fix it mine did the same till i got a new OS 18 engine that seemed to fix all the problems i was having. T-Maxx