No. 8 Engine Runs Rough/Rolling Idle [MZI-3.7]: Notes

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DESCRIPTION AND POSSIBLE CAUSE

8	ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION	Engine speed fluctuates between specified idle speed and lower speed and engine shakes excessively Idle speed is too slow and engine shakes excessively.
POSSIBLE CAUSE	Air leakage from intake-air system parts A/C system operation is improper Erratic signal to ignition coil Spark plug malfunction Ignition system improper operation 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 A/F sensor) 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) WARNING: The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read following warnings before servicing the fuel system: Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel. Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" described in this Service Information. (See BEFORE SERVICE PRECAUTION [MZI-3.7] .) (See AFTER SERVICE PRECAUTION [MZI-3.7] .) CAUTION: Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

ENGINE RUNS ROUGH/ROLLING IDLE

DESCRIPTION

Engine speed fluctuates between specified idle speed and lower speed and engine shakes excessively
Idle speed is too slow and engine shakes excessively.

POSSIBLE CAUSE

Air leakage from intake-air system parts
A/C system operation is improper
Erratic signal to ignition coil
Spark plug malfunction
Ignition system improper operation
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 A/F sensor)
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)
WARNING:
The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read following warnings before servicing the fuel system:
- Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
- Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE SERVICE PRECAUTION" and "AFTER SERVICE PRECAUTION" described in this Service Information.
  (See BEFORE SERVICE PRECAUTION [MZI-3.7] .)
  
  (See AFTER SERVICE PRECAUTION [MZI-3.7] .)
CAUTION:
- Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.