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: Exhaust system
EXHAUST SYSTEM INSPECTION Start the engine and inspect each exhaust system component for exhaust gas leakage. If leakage is found, repair or replace as necessary. EXHAUST SYSTEM REMOVAL/INSTALLATION Warning When the engine and exhaust system are hot, they can badly burn. Turn off t ...

Mazda 6 Service Manual: Contact Authorized Mazda Dealer and Have Vehicle Inspected
If any of the following warning lights or the indicator light turns on/flashes, the system may have a malfunction. Contact an Authorized Mazda Dealer to have your vehicle inspected. ...