Mazda 6 Service Manual: No.6 cranks normally but will not start

No.5 engine stalls-after start/at idle

No.7 slow return to idle

Other materials:

Mazda 6 Service Manual: Curtain Air Bags
The curtain air bags are mounted in the front and rear window pillars, and the roof edge along both sides. When the air bag crash sensors detect a side impact of greater than moderate force, the curtain air bag inflates quickly and helps to reduce injury mainly to the rear outboard passenger' ...

Mazda 6 Service Manual: Engine Exhaust (Carbon monoxide)
WARNING Do not drive your vehicle if you smell exhaust gas inside the vehicle: Engine exhaust gas is dangerous. This gas contains carbon monoxide (CO), which is colorless, odorless, and poisonous. When inhaled, it can cause loss of consciousness and death. If you smell exhaust gas inside the ...