Engine Runs Rough/Rolling Idle [PYUL]: Outline
WARNING: This page is about a different variant/trim than selected.
ENGINE RUNS ROUGH/ROLLING IDLE (PYUL) 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 detects DTCs
- PCM input signal error
- APP sensor or related wiring harness malfunction
- ECT sensor or related wiring harness malfunction
- MAF sensor or related wiring harness malfunction
- MAP sensor or related wiring harness malfunction
- A/F sensor or related wiring harness malfunction
- HO2S or related wiring harness 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
- CKP sensor input signal malfunction
- Poor installation
- Damaged trigger wheel (crankshaft pulley)
- Open or short circuit in related wiring harness
- CMP sensor input signal error
- Poor installation
- Damaged trigger wheel (intake camshaft)
- Damaged trigger wheel (exhaust camshaft)
- Open or short circuit in related wiring harness
|
| Possible cause |
- Inadequate fuel pressure (high or low pressure side)
- Fuel pressure sensor or related wiring harness 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 (built-into fuel pump unit)
- Fuel pump unit malfunction
- Improper operation of electric variable valve timing control system
- 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 restricted
- PCV valve malfunction
- Injector driver (built-into PCM) 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.
- 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. (Refer to [ BEFORE SERVICE PRECAUTION
] in Service Information.)
- 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.
- Fuel is highly flammable and dangerous. Fuel line spills and leakage can cause serious injury or death, and damage to equipment. Always Refer to [ QUICK RELEASE CONNECTOR REMOVAL/INSTALLATION (FUEL SYSTEM)
] before performing the fuel hose installation, and execute the [Fuel Leakage Inspection] after installation. (Refer to [ QUICK RELEASE CONNECTOR (FUEL SYSTEM) REMOVAL/INSTALLATION
] in Service Information). (Refer to [ AFTER SERVICE PRECAUTION
] in Service Information.)
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.
|
 Courtesy of MAZDA MOTORS CORP.
|
| 1 |
PCM |
| 2 |
Spill valve control solenoid valve (High pressure fuel pump) |