2005 Mazda3 clatter when cold - video included
 

Hey everyone. My car has been making this intermittent clatter noise. It usually only does it when it's cold out, at a stop light, in drive with brakes on. Might be related to the defroster/compressor turning on. It's almost impossible for me to diagnose the problem under these conditions so hopefully someone here can help me out! I made a video of the noise. I'm pulling up to a stop light and the noise starts, goes away, then comes back. The motor starts to vibrate a little more while making the noise. It's pretty loud. Loud enough for the car next to me to look over. Almost sounds like an exhaust leak...bad motor mount?? I used to have crappy idle but a new purge valve helped that out A LOT, though it's still not like is was when new. THANK YOU!

honestly form the video, it sounds like a ping... Where have you been getting gas??? Try running it doen to empty (almost) and going to a diff gas station. Try chevron or something. Just put like $20 in to see if thats it. Might be carbon build up causing it if that is it. I have used seafoam on mine and it helps. Some in the gas, some in the TB. I cant tell how loud it really is but the only other thing it woul dbe is like the A/C clutch??? does it happen when you are driving or just at idle like this?

Hey there, thanks for the reply. It's been doing this for a while now... many tanks of gas from different stations. I've cleaned my TB, doesn't sound like it's coming from there. It sounds kind of like an exhaust leak or maybe bad engine mounts. But I replaced my drivers side mount not THAT long ago and don't see it leaking now.... but who knows.

SO I drove home today with the AC on and it doesn't make the loud noise, however it does idle a little rougher. Maybe the metal in the exhaust manifold is cold in the morning and rattle but expands later in the day and when the car warms up so it doesn't do it???? I don't hear anything when Im driving. Only when stopped, and I think only when in drive at a stop light. Thanks