What Could Be the Reason for Feeling Less Power After Changing Spark Plugs?

[DelMaya]

The reasons for feeling less power after changing spark plugs may include: The spark plugs were not tightened properly; The replaced spark plugs are of the wrong model; There is an issue with the ignition coil. Effects of damaged spark plugs: If the spark plugs are damaged, it can directly cause various problems such as leakage in the vehicle's ignition system, increased fuel consumption, and reduced power. The most significant issue is difficulty in ignition, affecting the normal use of the vehicle. Severe erosion of the spark plugs, scarring at the top, damage, or melting and erosion of the electrodes indicate that the spark plugs are damaged and should be replaced. How to determine if spark plugs are damaged: Remove the spark plugs and observe their appearance to assess their condition. Normal spark plugs have an insulator skirt and electrodes that appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a reddish-brown insulator skirt, with an electrode gap between 0.8-0.9mm and no signs of electrode burn. If the spark plugs are covered in oil or deposits but are not damaged, they can continue to be used after cleaning off the oil and deposits. If the spark plugs are severely damaged, showing signs such as scarring, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plugs with new ones. Additionally, if the spark plugs appear black as if smoked, it indicates that the wrong heat range was selected or that the mixture is too rich, with oil seeping up.

[VonKira]

Just changed the spark plugs and found the car is slower to accelerate and lacks power? I've encountered this situation before. The main reason might be that the wrong spark plug model was selected, such as a heat range that doesn't match the engine's requirements, which can actually worsen ignition performance. Installation also matters; if they're too loose, there might be air leaks, and if too tight, the spark plugs can get deformed. Also, whether the surrounding wiring harness was disturbed during the replacement is crucial. Last time I removed and installed them, I accidentally loosened the ignition coil connector, causing the computer to report an error and resulting in reduced power. There's also a hidden reason: if the old spark plugs were used for too long, the engine had already adapted to that ignition state. Suddenly switching to new spark plugs requires a relearning and matching process, so it's normal to feel sluggish when driving during this period.

[VanAlejandro]

After replacing the spark plugs, feeling a lack of power is likely a compatibility issue. The electrode gaps of spark plugs vary significantly between brands—for instance, NGK and Bosch have different standards. If the gap is too large, the ignition will be weak. It's also crucial to apply precise torque during installation; using a torque wrench is the safest approach. Additionally, check the condition of the ignition coils. Old coils paired with new spark plugs might not deliver sufficient voltage, revealing underlying coil aging issues. I recommend also inspecting the cylinder pressure. If there's insufficient compression, new spark plugs can exacerbate the problem. Recently, a Ford I worked on had the owner complaining about reduced power after changing spark plugs. It turned out a small crack in the vacuum tube during reassembly caused insufficient air intake.

[LaylaRose]

The reason for the lack of power after replacing spark plugs is worth investigating. First, rule out model issues, such as mistakenly using ordinary spark plugs in turbocharged cars, which is definitely not acceptable. Installation details are also crucial; grease on the ceramic body can cause leakage. Additionally, consider the impact of other systems, such as the viscosity of the engine oil changed at the same time being too high, or gum deposits in the fuel system clogging the injectors. The most bizarre situation I've encountered was a car owner buying aftermarket parts to save money, where the electrode material had poor thermal conductivity, causing the spark to weaken during rapid acceleration. It's recommended to use a diagnostic tool to check the ignition data stream; misfires or abnormal ignition timing can be spotted at a glance.