What Causes Intermittent Engine Misfiring in Cars?
2 Answers
The reasons for intermittent engine misfiring in cars are: 1. Faults in the ignition system and fuel injection system; 2. Carbon buildup in the engine; 3. Wear and tear of cylinder wires. Engine misfiring refers to the condition where one cylinder fails to operate during engine operation, resulting in severe shaking during acceleration, lack of power, and abnormal noises. Symptoms of engine misfiring include: 1. Significant decrease in power; 2. Shortened lubrication oil usage cycle; 3. Prone to stalling and emitting black smoke. Methods to diagnose engine misfiring are: 1. Observe if the car body shakes violently at idle; 2. Check if there is obvious intermittency in the exhaust pipe airflow; 3. Severe body shaking and lack of power when accelerating below 2000rpm.
I encountered this situation over a decade ago. While driving, the engine suddenly started jerking severely with noticeable misfiring, but then it smoothed out after a while as if nothing had happened. Back then, I found out it was caused by severe carbon buildup on the spark plugs leading to intermittent ignition failures, especially more frequent during rainy or humid conditions. Another possible cause could be the degraded insulation performance of the ignition coils when heated, causing the engine to stall when hot but recover after cooling down. Loose wiring connections are also a common culprit—bumps and vibrations on rough roads can make the contacts intermittent. I recommend using an OBD scanner to read the fault codes for diagnosis as soon as possible; otherwise, it could lead to skyrocketing fuel consumption and damage to the catalytic converter. Don’t skimp on regular maintenance—replacing spark plugs periodically can prevent these issues and save you from costly repairs later.
