1. Build the vehicle (battery, spark-plug, wheels..)
2. Drive it for some distance
3. Leave the vehicle with the engine off (or turn off the engine than take the battery/spark-plug off)
4. Comeback to the vehicle, start the engine, put the good speed and try to drive (or put the battery/spark-plug back, start the engine, put the good speed and try to drive)
5. You will see the wheels rotating, but the vehicle won't move (like it's freeze in the air)

I found some ways to fix it :

1- Comeback some hours later (but somestimes it doesn't work..)
2- Let someone else to sit at the driver's seat

and by miracle the car can move again !