What are the symptoms of bad spark plugs? – Jalopnik

There are many different types of spark plugs, but they all do one job: igniting the air-fuel mixture in the cylinders. A shiny new spark plug does that consistently at the right intervals. The problems start when spark plugs start to wear out over time. Reliability is lost when the spark is interrupted and weakened by eroded electrodes and the build-up of carbon deposits. When this happens, combustion can malfunction and the engine can quickly show red flags.

If your spark plugs are nearing the end of the line, you may notice something is wrong when you try to start the engine. Long starts and rough idling are some not-so-subtle signs you may encounter. Cold starts are particularly damaging to ignition, and a worn spark plug simply doesn’t have enough energy to meet those extra demands. Even if you somehow manage to start the engine, there are misfires. This is when an engine experiences a temporary loss of power and erratic operation due to the fuel in the cylinder not igniting properly.

As the spark plugs wear, the symptoms become more noticeable under load. Your car may no longer respond as well as it used to when you press the accelerator, and it can be difficult to keep up with gear changes when merging or trying to pass someone. This sudden sluggishness when accelerating is one of the most common complaints, and can be due to the cylinders not working properly and having a negative effect on engine power.

If your spark plugs fail to ignite the air-fuel charge consistently, this can also decrease fuel economy. The injectors do not stop sending fuel to the cylinders even if the combustion of the previous charge is incomplete or delayed, which can ultimately lead to higher fuel consumption. When this happens, a full tank will not last as long as it used to.

Improper sparking can also cause the fuel to ignite when it isn’t supposed to, causing knocking or rattling noises. Engine rocking or jerking can also be associated with the above failures. Uneven power delivery is often the culprit behind rising problems, and it happens when spark quality takes a hit and the engine sucks in more air than it needs.

A modern vehicle can tell you something is wrong with it in several ways. One of those warnings is the check engine light (CEL). Although the CEL does not specifically identify faulty spark plugs, it often points out the symptoms of worn spark plugs, such as engine misfires. Flashing lights can indicate ongoing misfires that could damage the emissions components, which is why they are particularly bad news. Treat the problem immediately as soon as you see it.

Physical damage is also a strong sign of faulty spark plugs. Black deposits on the plug tip indicate carbon buildup and can cause incomplete combustion. Oil contamination, an oily residue on the insulator and electrodes, often indicates an internal oil leak. Damage to the electrode can be confirmed by signs of melting or erosion, all of which produce weak sparks. Cracks in the ceramic insulator can prevent proper electrical regulation and cause intermittent ignition failure.

If you ignore these symptoms, minor inflammatory problems can spread. Misfires force the engine to work harder and increase exhaust emissions. Over time, this additional strain can shorten the life of the engine and contribute to expensive repairs. So it is better to replace the spark plugs at the first sign of problems. Also make sure you use the correct ones for your vehicle, as the wrong spark plugs bring their own problems to your engine.