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2014 - Mazda6 - Engine

NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [SKYACTIV-G 2.5]



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

  • Engine overheating

  • PCM DTC is stored

  • Erratic signal to PCM

    • APP sensor or related circuit malfunction

    • ECT sensor No.1 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 air/fuel mixture ratio control operation

  • 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

  • Unbalanced fuel injection amount for each cylinder

  • 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 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

  • Erratic signal from CKP sensor

    • Loose installation

    • Damaged trigger wheel (crankshaft pulley)

    • Open or short circuit in related wiring harness

  • Inadequate fuel pressure (high or low pressure side)

    • 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 (built-into high pressure fuel pump) malfunction

    • Relief valve (built-into high pressure fuel pump) malfunction

    • Fuel pump (low-side) body mechanical malfunction

    • Fuel filter clogged

    • Fuel injector 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 or excessive unbalance for each cylinder

  • Improper intake valve timing

  • Improper exhaust valve timing

  • Spark plug malfunction

  • Incorrect signal to ignition coil

  • Exhaust system or TWC restricted

  • 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.

  • 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 SERVICE PRECAUTION” and “AFTER SERVICE PRECAUTION” described in this manual. (See BEFORE SERVICE PRECAUTION [SKYACTIV-G 2.5].) (See AFTER SERVICE PRECAUTION [SKYACTIV-G 2.5].)

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 matter.

CAUTION:

Related PIDs

Item (definition)

Unit/Condition

Definition

Condition/Specification (Reference)

AC_REQ

Off/On

A/C request signal

  • A/C switch off: Off

  • A/C switch on: On

APP1

%

APP sensor No.1

  • Accelerator pedal released: Approx. 15%

  • Accelerator pedal depressed: Approx. 82%

V

  • Accelerator pedal released: Approx. 0.75 V

  • Accelerator pedal depressed: Approx. 4.1 V

APP2

%

APP sensor No.2

  • Accelerator pedal released: Approx. 7.45%

  • Accelerator pedal depressed: Approx. 41%

V

  • Accelerator pedal released: Approx. 0.38 V

  • Accelerator pedal depressed: Approx. 2.05 V

ECT

°C, °F

Engine coolant temperature (No.1)

  • Displays ECT

V

  • ECT is 20 °C {68 °F}: Approx. 3.10 V

  • ECT is 40 °C {104 °F}: Approx. 2.16 V

  • ECT is 60 °C {140 °F}: Approx. 1.40 V

  • ECT is 80 °C {176 °F}: Approx. 0.87 V

  • ECT is 100 °C {212 °F}: Approx. 0.54 V

FUEL_PRES

KPa {MPa}, mBar {Bar}, psi, in H20

Fuel pressure

  • Displays fuel pressure

V

  • Fuel pressure is 3.0 MPa {31 kgf/cm2, 435 psi}: Approx. 0.92 V

  • Fuel pressure is 4.8 MPa {49 kgf/cm2, 696 psi}: Approx. 1.17 V

LOAD

%

Engine load

  • Idle (after warm up): Approx. 17.64%

  • Racing (engine speed is 2,000 rpm): Approx. 14.51%

  • Racing (engine speed is 4,000 rpm): Approx. 21.17%

LONGFT1

%

Long term fuel trim

  • Idle (after warm up): Approx. -2.34%

  • Racing (engine speed is 2,000 rpm): Approx. -0.78%

  • Racing (engine speed is 4,000 rpm): Approx. -0.78%

MAF

g/Sec

Mass air flow

  • Displays MAF

V

  • Switch ignition ON (engine off) (MAF: 0.59 g/s {0.078 lb/min}): Approx. 0.72 V

  • Idle (after warm up) (MAF: 2.17 g/s {0.287 lb/min}): Approx. 0.86 V

  • Racing (engine speed is 2,000 rpm) (MAF: 4.73 g/s {0.626 lb/min}): Approx. 1.07 V

MAP

KPa {MPa}, mBar {Bar}, psi, in H20

Manifold absolute pressure

  • Displays MAP

V

  • Switch ignition ON (engine off) (MAP:101 kPa {1.03 kgf/cm2, 14.6 psi}): Approx. 4.07 V

  • Idle (after warm up) (MAP: 33 kPa {0.34 kgf/cm2, 4.8 psi}): Approx. 1.34 V

  • Racing (engine speed is 2,000 rpm) (MAP: 26 kPa {0.27 kgf/cm2, 3.8 psi}): Approx. 1.05 V

O2S11

µA

A/F sensor

  • Idle (after warm up): Approx. -39 µA

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 3.84 mA

O2S12

V

HO2S

  • Idle (after warm up): 0—1.0 V

  • Deceleration fuel cut (accelerator pedal released from engine speed of 4,000 rpm or more): Approx. 0 V

RPM

RPM

Engine speed

  • Displays engine speed

SHRTFT1

%

Short term fuel trim

  • Idle (after warm up): Approx. 1.56%

  • Racing (engine speed is 2,000 rpm): Approx. -3.12%

  • Racing (engine speed is 4,000 rpm): Approx. -8.59%

TP REL

%

Throttle position signal (relative value)

  • Accelerator pedal released: Approx. 12%

  • Accelerator pedal depressed: Approx. 82%

VSS

KPH, MPH

Vehicle speed

  • Displays vehicle speed

Diagnostic Procedure

STEP

INSPECTION

RESULTS

ACTION

1

 VERIFY IF MALFUNCTION INCLUDES HARD ENGINE STARTING

  • Verify the vehicle engine condition.

  • Can idling be maintained?

Yes

Go to the next step.

No

Perform the symptom troubleshooting “NO.5 ENGINE STALLS-AFTER START/AT IDLE”.

(See NO.5 ENGINE STALLS-AFTER START/AT IDLE [SKYACTIV-G 2.5].)

2

 VERIFY IF MALFUNCTION CAUSE IS OVERHEATING

  • Access the ECT PID using the M-MDS.

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5].)

    CAUTION:

    • While performing this step, always operate the vehicle in a safe and lawful manner.

    • When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.

  • Is the ECT PID value less than 116 °C {241 °F} during driving?

Yes

Go to the next step.

No

The cause of this concern could be from the cooling system overheating.

3

 VERIFY PCM DTC

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [SKYACTIV-G 2.5].)

No

Go to the next step.

4

 VERIFY CURRENT INPUT SIGNAL STATUS

CAUTION:

  • While performing this step, always operate the vehicle in a safe and lawful manner.

  • When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.

Yes

Go to the next step.

No

APP1, APP2 PIDs are not as specified:

ECT PID is not as specified:

MAF PID is not as specified:

MAP PID is not as specified:

O2S11, SHRTFT1, LONGFT1 PIDs are not as specified:

O2S12 PID is not as specified:

Repair or replace the malfunctioning part according to the inspection results.

5

 DETERMINE IF MALFUNCTION CAUSE IS A/C REQUEST SIGNAL OR OTHER

  • Access the AC_REQ PID using the M-MDS.

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5].)

  • Monitor the AC_REQ PID while turning on and off the air conditioner using the switch on the control panel.

  • Does the AC_REQ PID value change from on to off according to switch control panel?

Yes

Go to the next step.

No

If the AC_REQ PID is always ON:

If the AC_REQ PID is always OFF:

6

 INSPECT A/C CUT-OFF CONTROL SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

7

 INSPECT DRIVE-BY-WIRE CONTROL SYSTEM OPERATION

Yes

Visually inspect the throttle body (damage/scratching).

  • If there is any malfunction:

    • Repair or replace the malfunctioning part according to the inspection results.

  • If there is no malfunction:

    • Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

8

 INSPECT FUEL INJECTOR OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

9

 INSPECT PURGE CONTROL SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

10

 INSPECT RELATED PART CONDITION

Yes

Service if necessary.

  • Repeat this step.

No

Go to the next step.

11

 INSPECT FUEL PRESSURE (HIGH-SIDE)

  • Start the engine and warm it up completely.

  • Access the FUEL_PRES PID using the M-MDS at idle.

    (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5].)

  • Is the FUEL_PRES PID value approx. 3 MPa {31 kgf/cm2, 435 psi}?

Yes

Go to Step 15.

No

Lower than 3 MPa {31 kgf/cm2, 435 psi}:

Higher than 3 MPa {31 kgf/cm2, 435 psi}:

  • Go to the next step.

12

 DETERMINE IF MALFUNCTION CAUSE IS FUEL PRESSURE SENSOR OR HIGH PRESSURE FUEL PUMP

  • Is the vehicle acceleration performance normal?

Yes

Go to the next step.

No

Go to Step 14.

13

 INSPECT FUEL PRESSURE SENSOR

Yes

Replace the fuel distributor.

(See FUEL INJECTOR REMOVAL/INSTALLATION [SKYACTIV-G 2.5].)

No

Go to Step 15.

14

 INSPECT SPILL VALVE CONTROL SOLENOID VALVE CONTROL CIRCUIT FOR SHORT TO GROUND

  • Switch the ignition off.

  • Disconnect the high pressure fuel pump and PCM connectors.

  • Inspect for continuity between high pressure fuel pump terminal A (wiring harness-side) and body ground.

  • Is there continuity?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between high pressure fuel pump terminal A and PCM terminal 1EE.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has a short to ground.

If the malfunction remains:

No

Replace the high pressure fuel pump.

(See HIGH PRESSURE FUEL PUMP REMOVAL/INSTALLATION [SKYACTIV-G 2.5].)

15

 INSPECT FUEL PRESSURE (LOW-SIDE)
    Specification:

  • 405—485 kPa {4.13—4.94 kgf/cm2, 58.8—70.3 psi}

Yes

Go to the next step.

No

Inspect the following:

  • Fuel line restriction

  • Fuel filter clogged

16

 INSPECT HYDRAULIC VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

17

 INSPECT ENGINE COMPRESSION
    Specification:

  • Compression

    • Standard: 954 kPa {9.73 kgf/cm2, 138 psi} (300 rpm)

    • Minimum: 763 kPa {7.78 kgf/cm2, 111 psi} (300 rpm)

    • Maximum difference between cylinders: 161 kPa {1.64 kgf/cm2, 23.4 psi} (300 rpm)

NOTE:

  • Because the SKYACTIV-G 2.5 retards the intake valve closing timing, compression pressure is low.

Yes

Go to the next step.

No

Inspect the following:

  • Damaged valve seat

  • Worn valve stem and valve guide

  • Worn or stuck piston ring

  • Worn piston, piston ring or cylinder

  • Improper intake valve timing

  • Improper exhaust valve timing

Service if necessary.

18

 INSPECT IGNITION SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace the malfunctioning part according to the inspection results.

19

 INSPECT EXHAUST SYSTEM FOR RESTRICTION

  • Inspect for restriction in the exhaust system and the TWC.

  • Is there any restriction?

Yes

Repair or replace the malfunctioning part according to the inspection results.

No

Go to the next step.

20

 INSPECT IF MALFUNCTION CAUSE IS PCV VALVE OR INJECTOR DRIVER (PCM INTEGRATED)

Yes

Replace the PCV valve.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [SKYACTIV-G 2.5].)

No

Injector driver malfunction.

If the problem remains, overhaul the engine.

21

Verify the test results.

  • If normal, return to the diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX [SKYACTIV-G 2.5].)

  • If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.

    • If the vehicle is repaired, troubleshooting is completed.

    • If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.



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