Mazda 6 Service Manual: No.7 slow return to idle

No.6 cranks normally but will not start

No.8 engine runs rough/rolling idle

Other materials:

Mazda 6 Service Manual: No. 1 one or more on-board diagnostic functions inoperative
When performing an asterisked (*) troubleshooting inspection, shake the wiring harness and connectors while doing the inspection to discover whether poor contact points are the cause of any intermittent malfunctions. If there is a problem, check to make sure connectors, terminals and wir ...

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 ...