Mazda 6 Service Manual: No.20 noise occurs at idle when vehicle is stopped in all positions/ranges

No.19 excessive shift shock on torque converter clutch (tcc)

No.21 noise occurs at idle when vehicle is stopped in d, s, l ranges, or in r position

Other materials:

Mazda 6 Service Manual: Intake-air system removal/installation
Warning When the engine and intake-air system are hot, they can badly burn. Turn off the engine and wait until they are cool before removing the intake-air system. Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from ...

Mazda 6 Service Manual: Starting a Flooded Engine
If the engine fails to start, it may be flooded (excessive fuel in the engine). Follow this procedure: 1. If the engine does not start within five seconds on the first try, wait ten seconds and try again. 2. Make sure the parking brake is on. 3. Depress the accelerator all the way and hold it ...