No. 8 Engine Runs Rough/Rolling Idle: Notes

POSSIBLE CAUSES DESCRIPTIONS

8	ENGINE RUNS ROUGH/ROLLING IDLE
DESCRIPTION	Engine speed fluctuates between the specified idle speed and lower speed and, engine shakes excessively. Idle speed is too slow and the engine shakes excessively.
POSSIBLE CAUSE	Air leakage from intake-air system A/C system improper operation Erratic signal to ignition coil Spark plug malfunction Purge solenoid valve malfunction Improper operation of electronic throttle control system EGR valve malfunction Low engine compression or excessive unbalance for each cylinder Improper valve timing Improper variable valve timing control system Poor fuel quality PCV valve malfunction Intake-air system restriction Exhaust system or three-way catalytic converter (TWC) restriction or clogging Disconnected electrical connectors Inadequate fuel pressure (high or low pressure side) Fuel pressure sensor or related circuit malfunction Spill valve control solenoid valve malfunction (built-in high pressure fuel pump) Relief valve malfunction (built-in delivery pipe) Fuel pump (low-side) body mechanical malfunction Fuel filter restriction or clogging Fuel leakage Incorrect fuel injection timing Unbalanced fuel injection amount for each cylinder High pressure fuel pump malfunction Fuel injector malfunction Erratic signal from CKP sensor Erratic or no signal from CMP sensor ECT sensor or related circuit malfunction Manifold absolute pressure (MAP) sensor or related circuit malfunction Accelerator position sensor or related circuit malfunction MAF sensor malfunction Incorrect or no load signal input Engine overheating Vacuum leakage Injector driver module or related circuit malfunction WARNING: The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services: 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 injury 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 manual. (See AFTER REPAIR PROCEDURE ). (See BEFORE REPAIR PROCEDURE ). CAUTION: Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the 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 the specified idle speed and lower speed and, engine shakes excessively.
Idle speed is too slow and the engine shakes excessively.

POSSIBLE CAUSE

Air leakage from intake-air system
A/C system improper operation
Erratic signal to ignition coil
Spark plug malfunction
Purge solenoid valve malfunction
Improper operation of electronic throttle control system
EGR valve malfunction
Low engine compression or excessive unbalance for each cylinder
Improper valve timing
Improper variable valve timing control system
Poor fuel quality
PCV valve malfunction
Intake-air system restriction
Exhaust system or three-way catalytic converter (TWC) restriction or clogging
Disconnected electrical connectors
Inadequate fuel pressure (high or low pressure side)
Fuel pressure sensor or related circuit malfunction
Spill valve control solenoid valve malfunction (built-in high pressure fuel pump)
Relief valve malfunction (built-in delivery pipe)
Fuel pump (low-side) body mechanical malfunction
Fuel filter restriction or clogging
Fuel leakage
Incorrect fuel injection timing
Unbalanced fuel injection amount for each cylinder
High pressure fuel pump malfunction
Fuel injector malfunction
Erratic signal from CKP sensor
Erratic or no signal from CMP sensor
ECT sensor or related circuit malfunction
Manifold absolute pressure (MAP) sensor or related circuit malfunction
Accelerator position sensor or related circuit malfunction
MAF sensor malfunction
Incorrect or no load signal input
Engine overheating
Vacuum leakage
Injector driver module or related circuit malfunction
WARNING:
The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
- 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 injury 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 manual.
  (See AFTER REPAIR PROCEDURE ).
  
  (See BEFORE REPAIR PROCEDURE ).
CAUTION:
- Disconnecting/connecting the quick release connector without cleaning it may possibly cause damage to the fuel pipe and quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.