2000 Toyota Tazz unussual sound

My car Toyota Tazz 1.3 2E engine has changed its sound, I thought it was plugs but I changed them including its cables but the sound is still unusual. Can the tarperts affect the sound? The sound is normal when I'm driving but when its on the neutral gear that's when the sound changes. When I'm taking-off plugs one-by-one while the engine is running, plug number 2 makes no different.