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: Tire Rotation
WARNING Rotate tires periodically: Irregular tire wear is dangerous. To equalize tread wear for maintaining good performance in handling and braking, rotate the tires every 12,000 km (7,500 miles). However Mazda recommends to rotate every 8,000 km (5,000 miles) to help increase tire life and ...

Mazda 6 Service Manual: Engine control system operation inspection
Main Relay Operation Inspection Verify that the main relay clicks when the ignition switch is turned to ON position and off. If there is no operation sound, inspect the following. - Main relay (See RELAY INSPECTION.) - Harness and connector between ignition switch and main relay termi ...