Engine Runs Rough/Rolling Idle: Notes
ENGINE RUNS ROUGH/ROLLING IDLE (VIN Y) DESCRIPTION AND POSSIBLE CAUSE
| Troubleshooting item |
Engine runs rough/rolling idle |
| Description |
- Idle speed lower than the specification.
- Idling speed unstable, increases/decreases.
|
| Possible cause |
- Engine overheating
- PCM DTC is stored
- Erratic signal to PCM
- APP sensor or related circuit malfunction
- ECT sensor No. 1 or related circuit malfunction
- ECT sensor No. 2 or related circuit malfunction
- MAF sensor or related circuit malfunction
- MAP sensor or related circuit malfunction
- A/F sensor or related circuit malfunction
- HO2S or related circuit malfunction
- Improper load signal input
- Improper A/C request signal
- Improper operation of A/C system
- Improper operation of drive-by-wire control system
- Incorrect fuel injection timing
- Fuel injector malfunction
- Purge solenoid valve malfunction
- Poor fuel quality
- Air leakage from intake-air system
- Intake-air system restriction
- Electrical connector disconnected
- Fuel leakage
- Vacuum leakage
- Improper engine oil viscosity
- Erratic signal from CKP sensor
- Loose installation
- Damaged trigger wheel (crankshaft pulley)
- Open or short circuit in related wiring harness
- Erratic or no signal from CMP sensor
- Loose installation
- Damaged trigger wheel (intake camshaft and/or exhaust camshaft)
- Open or short circuit in related wiring harness
- Inadequate fuel pressure (high or low pressure side)
- High fuel pressure sensor or related circuit malfunction
- High pressure fuel pump malfunction
- Spill valve control solenoid valve control circuit malfunction (damage to driver in PCM caused by short circuit to ground system)
- Spill valve control solenoid valve malfunction (built-into high pressure fuel pump)
- Relief valve (built-into high pressure fuel pump) malfunction
- Fuel line restriction
- Fuel filter clogged
- Fuel pump unit malfunction
- Improper operation of electric variable valve timing control system (PCM DTC is stored.)
- Improper operation of hydraulic variable valve timing control system
- Low engine compression
- Improper intake valve timing
- Improper exhaust valve timing
- Spark plug malfunction
- Ignition coil malfunction
- Exhaust system and/or TWC restriction
- PCV valve malfunction
- Injector driver (built-into PCM) malfunction
|
| Possible cause |
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.
- Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the "Fuel Line Safety Procedure" to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION [(VIN Y) (US)]
.)
- Fuel may cause irritation if it comes in contact with skin and eyes.
- If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.
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.
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 Courtesy of MAZDA MOTORS CORP.
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CAUTION:
- Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.