6 Symptoms of Faulty Spark Plugs
Faulty spark plugs can cause misfires (one of the symptoms), so many of the common warning signs overlap. If you suspect your spark plugs are bad, you should have your vehicle inspected by a mechanic immediately.
1) Misfires
Misfires occur when there is a problem with the combustion of the air-fuel mixture in the cylinder. Misfires can occur if the mixture ignites too early, too late, or not at all.
Unburned fuel can cause increased exhaust fumes, which are harmful to the environment, and can cause a strong fuel smell in the exhaust. If the misfire is not corrected, engine damage is inevitable.
2) Rough and/or noisy idle (with vibration)
A vehicle with a defective spark plug may idle rough, make noise, or vibrate. This happens because unburned fuel from a misfire caused by a bad spark plug confuses the O2 sensor.
This removes fuel from the cylinders, making the mixture lean. Lean operation will result in rough idling and increased misfires. If the idle is rough, the RPMs may spike. This can be confirmed by checking the tachometer on the dashboard or by listening to the engine.
A higher tone is a higher speed, while a lower tone is a lower speed. The skipping is the result of the Engine Control Unit (ECU) trying to compensate for the problem.
3) Erratic or Slow Acceleration
An abnormal response to accelerator pedal pressure will be noticeable, especially when rapid acceleration is required. Hesitation when accelerating is another issue caused by misfiring, which makes the mixture lean. If you suddenly notice your car stalling or sputtering when you step on the accelerator, it may be a sign that you need new spark plugs.
4) Poor Fuel Economy
A rich mixture or misfiring cylinders creates inefficiency and waste. Because some of the fuel remains unburned in the vehicle or is burned in the wrong part of the system that does not perform, the vehicle has to use more fuel to maintain the performance level that the driver demands.
It is always a good idea to track your car’s fuel economy. There are many possible causes for high fuel consumption, but a sudden drop in fuel consumption may be an indication that your spark plugs are fouled or defective.
5) Difficulty Starting
Faulty spark plugs can cause your vehicle to stall or be difficult to start. Because it takes a relatively large amount of energy to overcome inertia when the car is stationary, your vehicle is likely to have the most problems during this time.
Spark plugs usually don’t all fail at the same time, so if your vehicle won’t start at all, it may be that your battery is the problem, not the spark plugs.
6) Check Engine Light
Faulty spark plugs will cause misfires and illuminate the check engine light on your dashboard. The ECU will generate codes that can be checked with an OBD2 reader on vehicles manufactured after 1996. A variety of radio related trouble codes may occur (e.g. DTC P0351 and DTC P0352).