What is the engine firing order?
2 Answers
The firing order of the engine is 1, 3, 4, 2: when cylinder 1 is in the power stroke, cylinder 3 is in the compression stroke, cylinder 4 is in the intake stroke, and cylinder 2 is in the exhaust stroke. The firing order depends on factors such as the engine structure, crankshaft design, and crankshaft load. The crankshaft is mentioned twice here, as the smoothness of the engine largely depends on the crankshaft. The centrifugal inertial force generated by the uneven rotating mass of the crankshaft can cause engine vibration. Therefore, the crankshaft throws (journals and the crank arms at both ends) should be as symmetrical and evenly distributed as possible. The two cylinders that fire consecutively should be spaced as far apart as possible, and in V-type engines, the left and right banks of cylinders should alternate firing. Thus, the engine must have a firing order that can balance the operation of the crankshaft.
I often study the basic principles of car engines. Simply put, the firing order of an engine refers to the sequence in which the cylinders ignite. For example, in a four-cylinder engine, the most common firing order is 1-3-4-2, meaning the first cylinder fires, followed by the third, then the fourth, and finally the second. This design ensures smoother engine operation by preventing all pistons from moving simultaneously, which would cause excessive vibration. If the firing order is disrupted, the engine will shake violently, leading to an uncomfortable driving experience and potential damage to components like spark plugs or bearings. I've seen different firing orders for engines with varying cylinder counts—for instance, a six-cylinder engine might follow a 1-4-2-6-3-5 sequence. The key is to adjust the order based on the cylinder layout to balance power output. The firing order also impacts fuel efficiency, as proper timing ensures more complete combustion, reducing wasted fuel. Overall, understanding the firing order is fundamental to diagnosing engine issues, helping you sense whether the engine is healthy at idle and prioritize checking the ignition module during routine maintenance.
