No.8 Engine Runs Rough/Rolling Idle: Notes

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

NO.8 DESCRIPTION AND POSSIBLE CAUSE

8	ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION	The engine speed fluctuates between the specified idle speed and a lower speed, and the engine shakes excessively. The idle speed is too slow and the engine shakes excessively.
POSSIBLE CAUSE	Vacuum leakage Air leakage from intake-air system parts Air suction at intake-air system (between MAF sensor and intake ports) Air cleaner restriction Air cleaner improper installation Improper operation of drive-by-wire control system (abnormal signals from APP sensor, TP sensor and load signal to PCM) SSV stuck open SSV solenoid valve malfunction (stuck open) APV stuck open* APV motor malfunction* Carbon or foreign materials on primary intake port APV position sensor malfunction* Poor fuel quality Inadequate fuel pressure Pressure regulator (integrated in fuel pump unit) malfunction Fuel pump body mechanical malfunction Fuel line restriction or clogging Fuel leakage from fuel injector Fuel injector (FP1) (RP1) malfunction (leakage, clogging, improper injector amount) Jet air mixing system malfunction (restriction or leakage in air passage) Restriction in exhaust system Improper operation of AIR system Purge solenoid valve malfunction (stuck open) Improper fuel injection control operation (abnormal signals from MAF, ECT and IAT sensors to PCM) Erratic signal from eccentric shaft position sensor Damaged or improper installed eccentric shaft position sensor pulse wheel Disconnected electrical connectors Improper load signal input Engine overheating Low engine compression Engine internal malfunction Abnormal engine oil condition (viscosity, deterioration) Low oil pressure Excessive fuel pressure Air mixed in oil line Metering oil pump malfunction Leakage or clogging in oil pipe Leakage or clogging in oil nozzle Excessive engine mechanical loss Metering oil pump improper operation (in fail-safe mode) A/C system operation is improper Spark leakage from high-tension leads Spark plug malfunction Improper spark plug heat range Ignition coil malfunction Improper ignition timing WARNING: The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read the 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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this article. (See BEFORE REPAIR PROCEDURE .) (See AFTER REPAIR PROCEDURE .) CAUTION: Disconnecting/connecting quick release connector without cleaning it may possibly 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

The engine speed fluctuates between the specified idle speed and a lower speed, and the engine shakes excessively.
The idle speed is too slow and the engine shakes excessively.

POSSIBLE CAUSE

Vacuum leakage
Air leakage from intake-air system parts
Air suction at intake-air system (between MAF sensor and intake ports)
Air cleaner restriction
Air cleaner improper installation
Improper operation of drive-by-wire control system (abnormal signals from APP sensor, TP sensor and load signal to PCM)
SSV stuck open
SSV solenoid valve malfunction (stuck open)
APV stuck open*
APV motor malfunction*
Carbon or foreign materials on primary intake port
APV position sensor malfunction*
Poor fuel quality
Inadequate fuel pressure
Pressure regulator (integrated in fuel pump unit) malfunction
Fuel pump body mechanical malfunction
Fuel line restriction or clogging
Fuel leakage from fuel injector
Fuel injector (FP1) (RP1) malfunction (leakage, clogging, improper injector amount)
Jet air mixing system malfunction (restriction or leakage in air passage)
Restriction in exhaust system
Improper operation of AIR system
Purge solenoid valve malfunction (stuck open)
Improper fuel injection control operation (abnormal signals from MAF, ECT and IAT sensors to PCM)
Erratic signal from eccentric shaft position sensor
Damaged or improper installed eccentric shaft position sensor pulse wheel
Disconnected electrical connectors
Improper load signal input
Engine overheating
Low engine compression
- Engine internal malfunction
- Abnormal engine oil condition (viscosity, deterioration)
- Low oil pressure
- Excessive fuel pressure
- Air mixed in oil line
- Metering oil pump malfunction
  - Leakage or clogging in oil pipe
  - Leakage or clogging in oil nozzle
Excessive engine mechanical loss
Metering oil pump improper operation (in fail-safe mode)
A/C system operation is improper
Spark leakage from high-tension leads
Spark plug malfunction
Improper spark plug heat range
Ignition coil malfunction
Improper ignition timing
WARNING:
The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read the 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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this article.
  (See BEFORE REPAIR PROCEDURE .)
  
  (See AFTER REPAIR PROCEDURE .)
CAUTION:
- Disconnecting/connecting quick release connector without cleaning it may possibly 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.