LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2012 >> 6 i Touring >> Repair and Diagnosis >> External Pages >> Different car >> Section 574 (Symptom Troubleshooting (Engine - MZI-3.7)) >> No. 8 Engine Runs Rough/Rolling Idle [MZI-3.7] >> Diagnostic procedure

Diagnostic procedure

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
STEP INSPECTION RESULTS ACTION
1 Warm up the engine
Idle the engine for 5 min.
Is the symptom disappeared?		 Yes Troubleshooting completed (Cause of this symptom is that the idle learning of electronic throttle control system is not completed)
No Go to the next step.
2 Verify the following:
  • External fuel shut off or accessory (such as kill switch, alarm)
  • Fuel quality (such as proper octane, contamination, winter/summer blend)
  • No air leakage from intake-air system
  • Proper sealing of intake manifold and components attached to intake manifold
  • Ignition wiring
  • Electrical connections
  • Fuses
  • Smooth operation of throttle valve
  • PCM GND circuit (1B, 1E, 1J)

Are all items normal?

 Yes Go to the next step.
No Service if necessary Repeat Step 2
3 Connect the M-MDS to the DLC-2.
Switch ignition to ON (Engine off).
Retrieve any DTCs.
Are there any DTCs displayed?		 Yes DTC is displayed: 
Go to the appropriate DTC inspection.
(See DTC TABLE [MZI-3.7] .)
No No DTC is displayed: 
Go to the next step
4 Is the engine overheating? Yes Go to symptom troubleshooting "No. 17 Cooling system concerns - Overheating".
(See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING [MZI-3.7] .)
No Go to the next step
5 Connect the M-MDS to the DLC-2.
Access MAF PID
Drive vehicle with monitoring PID. Is MAF PID within specification?		 Yes Go to the next step.
No Inspect for open or short circuit of MAF sensor and related wiring harness.
6
NOTE:
  • The following test is for engine running at rough idle with A/C on. If other symptoms exist, go to the next step.
Connect pressure gauge to A/C low and high pressure side lines.Start engine and idle it.Turn the A/C switch on.Measure low side and high side pressures.Are pressures within specifications?(See REFRIGERANT PRESSURE CHECK .)		 Yes Go to the next step.
No If the A/C is always on, go to symptom troubleshooting "No 24 A/C is always on or A/C compressor runs continuously".
(See NO. 24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [MZI-3.7] .)
For other symptoms, inspect the following:
  • Refrigerant charging amount
  • Condenser fan operation
7
NOTE:
  • The following test is for engine running rough with P/S on. If other symptoms exist, go to the next step.
Connect the M-MDS to the DLC-2.Start the engine and idle itAccess PSP PID.Is PSP PID within specification?		 Yes Go to the next step.
No Inspect power steering pressure switch operation and wiring harness between P/S pressure switch and PCM terminal 1G
8 Visually inspect the CKP sensor and teeth of crankshaft pulley.
Are the CKP sensor and teeth of crankshaft pulley normal?		 Yes Go to the next step.
No Replace the malfunctioning part
9 Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) for all cylinders.
Are wiring harness conditions normal?		 Yes Go to the next step
No Repair the wiring harnesses
10 Perform the spark test
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7] .)
Is a strong blue spark visible at each cylinder?		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the spark test result.
11 Inspect the spark plug condition
Is the spark plug wet, covered with carbon or grayish white?		 Yes Spark plug is wet or covered with carbon: 
Inspect for fuel leakage from injector.
Spark plug is grayish white: 
Inspect the fuel injector for clogging.
No Install the spark plugs on original cylinders.
Go to the next step
12 Perform the electronic throttle control system operation inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7] .) Does the electronic throttle control system function properly?		 Yes Go to the next step
No Repair or replace the malfunctioning part according to electronic throttle control system operation inspection results
13 Install fuel pressure gauge between fuel pipe and fuel distributor
Start the engine and run it at idle
Measure fuel line pressure during idle
Is fuel line pressure correct during idle?
(See FUEL LINE PRESSURE INSPECTION [MZI-3.7] .)		 Yes Go to the next step.
No Low: 
Perform "Fuel Pump Operation Inspection" and "Fuel Pump Control System Operation Inspection", repair or replace according to inspection results. Inspect the fuel line for clogging
If there is no malfunction, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7] .)
High: 
Perform "Fuel Pump Control System Operation Inspection", repair or replace according to inspection results.
If there is no malfunction, replace the fuel pump unit
(See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7] .)
14 Visually inspect for fuel leakage at fuel injector, O-ring, and fuel line
Service if necessary
Does fuel line pressure hold after ignition is turned off?
(See FUEL LINE PRESSURE INSPECTION [MZI-3.7] .)		 Yes Go to the next step.
No Inspect fuel injector.
If fuel injector is normal, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7] .)
15 Connect the M-MDS to the DLC-2
Start the engine and idle it.
Access LONG FT1 PID, LONG FT2 PID
Measure LONG FT1 PID, LONG FT2 PID at idle
Is PID value normal?		 Yes Go to the next step
No LONG FT1 PID, LONG FT2 PID is out of specification.
Less than specification (too rich):
  • Inspect EVAP control system.

    Greater than specification (too lean):

  • Inspect for air leakage at intake-air system components
  • If system is normal, go to the next step.
16 Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from purge solenoid valve side
Plug opening end of vacuum hose
Start the engine.
Does the engine condition improve?		 Yes Check if purge solenoid valve is stuck open mechanically.
Inspect EVAP control system.
No Go to the next step
17 Visually inspect the exhaust system part
Is there any deformed exhaust system part?		 Yes Replace the suspected part.
No Go to the next step.
18 Visually inspect the CMP sensor and teeth of camshaft
Are the CMP sensor and teeth of camshaft normal?		 Yes Go to the next step
No Replace the malfunctioning part.
19 Inspect variable valve timing control system operation (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7] .)
Does variable valve timing control system function properly?		 Yes Go to the next step.
No Repair or replace the malfunctioning part
20 Is engine compression correct? Yes Inspect PCV valve.
  • If the PCV valve is normal, inspect the valve timing.
No Inspect for causes.
21
  • Verify test results
    • If normal, return to diagnostic index to service any additional symptoms (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7] .)
    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis
      • If vehicle is repaired, troubleshooting completed
      • If vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available Retest
scientia non olet · About LEMON Manuals