What Causes Engine Idle Vibration After Replacing Spark Plugs?
2 Answers
The reasons for engine idle vibration after replacing spark plugs are: 1. The spark plug wires were broken or damaged during removal, causing abnormal ignition; 2. Incorrect spark plug installation, either not tightened properly or wires not fully inserted; 3. Aging ignition coils leading to performance degradation. The function of spark plugs is: to release the high-voltage pulses sent through the high-tension leads, ionizing the air between the two electrodes to create a spark that ignites the air-fuel mixture in the cylinder. The main types of spark plugs include: standard spark plugs, extended-nose insulator spark plugs, electrode-type spark plugs, gasket-type spark plugs, surface-gap spark plugs, and surface-discharge spark plugs.
I just learned how to change spark plugs, but now my car shakes like an earthquake at idle. It might be because the spark plugs weren't installed properly or the wrong type was selected, as spark plugs must fully match the original factory specs to ensure proper ignition. Incorrect gap size or loose torque can lead to uneven combustion. Loose connections can also cause this issue. The material of the spark plugs, such as iridium or platinum, makes a big difference—using the wrong type can disrupt the air-fuel ratio. I tried checking and adjusting the spark plug gap with a gap gauge myself, but ended up taking it to a repair shop where they fixed it in one go with professional tools. Unstable idle also affects fuel efficiency, so it's best to address it early to avoid damaging the catalytic converter.
