Mazda 6 Service Manual: No.4 hard to start/long crank/erratic start/erratic crank

No.3 will not crank

No.5 engine stalls-after start/at idle

Other materials:

Mazda 6 Service Manual: Idle air control (iac) valve inspection
Note Perform the following inspection only when directed. Operation Test Carry out the Idle Air Control Inspection. (See Idle Air Control System Inspection.) If not as specified, perform the further inspection for the IAC valve. Resistance Inspection 1. Disconnect the negative batt ...

Mazda 6 Service Manual: Underbody Maintenance
Road chemicals and salt used for ice and snow removal and solvents used for dust control may collect on the underbody. If not removed, they will speed up rusting and deterioration of such underbody parts as fuel lines, frame, floor pan, and exhaust system, even though these parts may be coated ...