[Toxicity]

As Mikep said you can't but an alternative is to freeze the player if the engine is off:

Код:

new engine[700]; //number of cars in the server (700 is maximum number of cars)
public OnPlayerCommandText(playerid, cmdtext[])
{
	if(strcmp(cmd, "/engine", true) == 0)//when they type /engine do this:
	{
		if (IsPlayerInAnyVehicle(playerid))//check if they are in a car
		{
			new vehicleId = GetPlayerVehicleID(playerid);//get the ID of the car the player is in
			if (GetPlayerState(playerid) != PLAYER_STATE_DRIVER)//if the player is not the driver
			{
				return SendClientMessage(playerid, , "You can't start/stop the engine, you're not the driver!");
			}
			if (engine[vehicleId] == 1)//if the car is on
			{
				engine[vehicleId] = 0;//set the car as off
				TogglePlayerControllable(playerid, 0);//set the player to be unable move
			}
			else if (engine[carid] == 0)//if the car is off
			{
				engine[vehicleId] = 1;//set the car as on
				TogglePlayerControllable(playerid, 1);//set the player to be able to move
			}
			return 1;
		}
	}
}

I don't know if this will work or not, try it.

PS: 0.o My first post on the sa-mp forums.
PPS: "plzz" is not a word. If I wasn't trying to beat Daren, I wouldn't have helped you. Use English in the future.