Rattling noise coming from my 2005 mazda 6's engine. it only happens when i drive slowly such as going through kfc drive through

moving noise is very hard to find.

could well be exhaust shields,
did you take a rubber mallet and tap the parts (exh, end to end?)
bang ,rattle, bang , repeat
seen many bad CAT (brick inside loose) rattle. hit it. bingo. there you go.

i also jam objects in cat shelds to stop them for making noise.
just for temporary to find source.

The noise could be due to worn universal joint on drive shaft. Could be going bad. Slowly starts as a rattle with a little vibration and over time it gets worse. If there's no propeller type drive shaft, running down the center under the car, then it is something else

Hi . Unfortunately it's a common problem with mazda6 engine.When they run low on oil the crank shaft tend to get damaged.And some times people tend to top up oil rather than changing oil between 6000 &10000kms .Yep the engine is seized cost less replacing the engine than repairing it.good luck....

Your heat shieid is ratting.

Could be something jumping around in the exhaust. Is your catalytic conv in that area?

Are you losing power as well? if so it sounds like the camshaft is worn, this can be confirmed with a compression test

one thing to check is rear engine mounting i have had a stone wedged in one and it causes a nasty noise when accelerating

Have you checked the catalytic converter (also reffered to as simply a Cat by mecanics)? It's the first big canister you encounter on the exhaust line right after the manifold and before the resonator and/or muffler. After a while rust and time can cause either the casing itself to come loose and rattle, or the insides themselves break up and rattle around the cat. And being where it is it often resonates sound around the engine compartment, making it seem the sound is coming from elsewhere than it actually is. And while your at it don't forget to check the flex pipe usually connected to the cat also (some models do not have a flex pipe though). If all that is fine, then the other things to check would be the accessory brackets, wire holders and the like. With vibration and time, sometimes they loosen up and start to rattle. Still nothing? check the suspension parts for anything loose (IE. sway bar links, coils springs, tie-rod, suspension tables). Other than that there isn't much in there that can rattle. If you look at how an engine is built, you'll see that there isn't much inside that can rattle around without causing the engine to fail altogether. I'm not saying it can't happen though, but it's highly improbable. Hope this helps

petrol or diesel

Check the heat shield on the catylitic converter,exhaust manifold. Kev-Mn