The firing order diagram determines the correct sequence to attach the spark plug wires from the distributor to the cylinders. Improper placement causes engine sputters that can stall a manual transmission. The transmission needs smooth engine operation to match the engine's revolutions per minute with the correct gear ratio.
The firing sequence of the distributor is fixed, but the firing order of the engine varies depending on the type of engine, its design and the number of cylinders it employs. Cylinders firing out of order can cause excessive vibration, incomplete combustion or a complete failure to fire. The cylinder firing drives the pistons down, turning the combustion energy into kinetic energy that rotates the vehicle's drive shaft, which is connected to the transmission.