Problem with R/C

Hey everybody, I was unaware that this site had an R/C forum. Its great that it does cuz I have a problem with my car and I was wondering if anybody has had the same problem and can fix it. I have a Tamiya TB01 4WD chassis that seems like the engine cuts off every now and then. If i'm driving it and hit the grass its like the car doesn't recieve any input from the remote. It turns but it won't move. My speed controller is fine, but its not soldered in. Could it be because of that? It always worked fine before. Thanks

i was round at my friends house a couple of weeks back...we got bored of revising so we took his tamiya opel vectra out into the garden. it had exactly the same problem...every time it went over a bump, the motor would stop working...everything else was fine and the servo was still moving the speed contoler. basicaly i played around with the speedo for a few minits...it turns out that the cente bolt on the speed contoler was very slightly loose...i tightened it up less than a quarter of a turn (it wouldnt tighten any more) and it worked fine.

hope that helps