1. Fuel mixture: The engine must receive the correct mixture of fuel and air in order to run properly. If the mixture is too rich or too lean, the engine will stall or run rough. The idle speed screw adjusts the amount of air that enters the engine, and the fuel injection system regulates the amount of fuel that is injected.
2. Spark timing: The spark plugs must fire at the correct time in order to ignite the fuel and air mixture. If the spark timing is too early or too late, the engine will run rough or stall. The distributor adjusts the spark timing.
3. Compression: The engine must have sufficient compression in order to properly ignite the fuel and air mixture. If the compression is too low, the engine will not have enough power and will stall. The piston rings and valves keep the compression from escaping from the cylinders.
4. Valves: The valves open and close to allow air and fuel into the cylinders, and to expel exhaust fumes. If the valves are not working properly, the engine will not run properly. The valve springs keep the valves closed, and the camshaft opens and closes the valves.
5. Electronic control unit (ECU): The ECU is the electronic brain of the engine. It controls the fuel injection, spark timing, and other engine functions. If the ECU is not working properly, the engine will not run properly.
