Mazda CX-9 Grand Touring 2009 Manual page 1333

NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [MZI-3.7]
NO.8 ENGINE RUNS ROUGH/ROLLING IDLE (MZI-3.7) DETECTION CONDITIONS AND
POSSIBLE CAUSES
8 ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION
POSSIBLE
CAUSE
2008 Mazda CX-9 Grand Touring
2008 ENGINE Symptom Troubleshooting (MZI-3.7) - Mazda CX-9
Engine speed fluctuates between specified idle speed and lower speed and
engine shakes excessively.
Idle speed is too slow and engine shakes excessively.
Air leakage from intake-air system parts
A/C system operation is improper
Erratic signal to ignition coil
Spark plug malfunction
Purge solenoid valve malfunction
Improper operation of electronic throttle control system
Idle learning of electronic throttle control system is not completed
Erratic or no signal from CMP sensor
Low engine compression
Improper valve timing
Improper variable valve timing control system operation
Erratic signal from CKP sensor
Improper air / fuel mixture ratio control operation (abnormal signal form MAF
sensor or HO2S)
Open or short circuit in PCM GND circuit
Poor fuel quality
PCV valve malfunction
Air cleaner restriction
Restriction in exhaust system
Disconnected electrical connectors
Inadequate fuel pressure
Fuel pump body mechanical malfunction
Improper load signal input
Fuel line restriction or clogging
Improper fuel injection control operation
Fuel leakage from fuel injector
Fuel injector clogging
Engine overheating
Vacuum leakage
Pressure regulator malfunction (built-in fuel pump unit)