What Causes Cylinder Misfire in a Three-Cylinder Engine?
3 Answers
There are mainly two reasons: 1. Damage to external components: Primarily caused by components around the combustion chamber such as valves, valve seat rings, valve guides, spark plugs, etc. 2. Misfire due to failure to ignite or delayed ignition of the air-fuel mixture in the cylinder: For the first scenario, typically check the spark plug, clean carbon deposits from the intake and exhaust valves, and inspect the turbocharger for any issues, such as wear or burn damage to the turbocharger impeller. For the second scenario, it is usually caused by an abnormality in a certain component or part, leading to unstable ECU regulation of the engine, failing to meet the theoretical values calibrated by the ECU, resulting in misfire.
Oh, I've seen plenty of cases of three-cylinder misfires, and they usually boil down to a few common issues. The most frequent culprit is spark plug problems—either carbon buildup blocking the electrodes or excessive electrode gap preventing ignition. Ignition coils are also notorious for failing, especially in cars over five or six years old, where high temperatures degrade the coil insulation, leading to short circuits. Last time I worked on a car, the three-cylinder injector was clogged like a sieve, unable to atomize fuel properly, resulting in incorrect air-fuel mixture and failed ignition. Low cylinder compression is another thing to check—leaky valves or worn piston rings can reduce compression ratio. Don’t overlook small details like oxidized or loose wiring harness connectors either; if the signal can’t get through, the whole cylinder shuts down.
Last time, my neighbor's car had a misfire in one of its three cylinders and was shaking like a tractor. I spent a long time helping him diagnose it. The main causes usually lie in the ignition system: spark plugs that have reached the end of their lifespan or have incorrect gaps, or aging ignition coils with unstable output. The fuel system also needs thorough inspection—clogged fuel injectors or insufficient fuel pump pressure can make the air-fuel mixture too lean to ignite. On the mechanical side, a leaking head gasket is the most troublesome, as high temperature and pressure compromise the cylinder seal, cutting cylinder pressure in half. Faulty sensors can also cause issues; a bad camshaft position sensor makes it hard for the ECU to control ignition timing, while a faulty crankshaft position sensor can't even read the RPM signal accurately. Small things like loose wiring harness connectors are often the easiest to overlook.