Spark Plugs Replaced Correctly?
 

I know what you are thinking, "How could anyone foul up this simple procedure?"

However... I replaced my plugs this weekend, taking extra care to torque them carefully so as not to damage the aluminum threads. The cars starts and accelerates fine, but when I let the engine and transmission slow the car down, I notice a "new" sound. It's very faint, but it sounds like a bird chirping, or someone tapping a couple of cobble-stones together. It's possible the car always made this noise and I never noticed it. Is it possible air is leaking past the plugs because they were not tightened enough?

Thanks for any advice!

Does it go with engine speed or wheel speed? My first thought is pebbles in your tire treads, the second is an arc jumping within a plug wire connection or between plug wires, the third is brake noise. I doubt it's air leaking past your spark plug threads. Can you hear the sound with your engine idling? With the engine running at night do you see electrical discharges (blue sparks) among the plug wires? Jim

Thanks Jim, I'll check for arcing between the plug wires. It's not the brakes or a rock in the tires, but those are great ideas.

When I rebuilt my engine there were three cylinders that were leaking gasses past the cylinder/head mating surface. Folks outside could hear them. So, I'd suggest checking torque on your head nuts (large barrel nuts in recesses in the heads).

No, gasses are not leaking past your spark plugs.