How to Determine Which Cylinder is Misfiring?
3 Answers
There are several main methods to determine which cylinder is misfiring: 1. Remove the ignition wires one by one. If the shaking worsens, it's not that cylinder; if there's no change, then that cylinder is misfiring. 2. Observe the exhaust pipe outlet. The exhaust gas flow from the car will show obvious intermittency. At the same time, the exhaust pipe will shake violently, and you can clearly hear a "popping" or thumping sound. 3. At low RPMs around 2000, the car body will shake noticeably, acceleration will be weak, and the shaking sensation actually decreases at higher RPMs. The main causes of engine misfiring are the following two situations: 1. Ignition system. If the contacts of the distributor cap in the ignition system are severely eroded, it can cause spark jumping, mostly occurring between the corresponding terminals on the cap, resulting in severe idle speed fluctuation and significant power loss. 2. Fuel injection system.
During my own repair work, I discovered an experienced method for determining which cylinder is misfiring. First, let the engine idle, then disconnect the high-voltage ignition wire of a certain cylinder. Listen to the sound—the cylinder where the engine sound changes significantly is the one misfiring. If you disconnect the ignition wire of a normal cylinder, there will be obvious shaking and sound changes. Conversely, if you find almost no change in sound after disconnecting, it means this cylinder hasn't been working at all. I've used this method to identify the problematic cylinder in just ten minutes. Remember to wear insulated gloves before testing. Operation details vary greatly between different car models. If you can't handle it yourself, it's recommended to seek professional repair services.
To diagnose a misfiring cylinder, try this method: Unplug the ignition coil of each cylinder one by one while observing the engine's response. A normally functioning cylinder will cause more noticeable engine vibration when disconnected, whereas a faulty cylinder will show little change in engine operation when its ignition coil is unplugged. Alternatively, you can use an infrared thermometer to measure the temperature of the exhaust manifold. A properly functioning cylinder will have a higher exhaust temperature, while a malfunctioning one will show a lower temperature compared to the others. This method requires professional equipment but is accurate.
