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Home >> Mazda >> 2012 >> 6 i Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Symptom Troubleshooting [Engine Control System - MZI 3.7 V6]) >> No. 11 Engine Stalls/Quits, Engine Runs Rough, Misses, Buck/Jerk, Hesitation/Stumble, Surges >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different variant/trim than selected.
STEP INSPECTION RESULTS ACTION
1 INSPECT RELATED PART CONDITION 
  • Verify the following:
    • Vacuum connection
    • Air cleaner element
    • No air leakage from intake-air system
    • No restriction of intake-air system
    • Proper sealing of intake manifold and components attached to intake manifold
    • Ignition wiring
    • Fuel quality (such as proper octane, contamination, winter/summer blend)
    • Electrical connections
    • Smooth operation of throttle valve
    • Engine mount installation
  • Are all items normal?
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
Repeat Step 1.
2 VERIFY PCM DTC 
  • Switch the ignition to ON (Engine off).
  • Retrieve any DTCs using the M-MDS.

    (See ON-BOARD DIAGNOSTIC TEST .)

  • Are there any DTCs displayed?
Yes DTC is displayed:
  • Go to the appropriate DTC inspection.

    (See DTC TABLE .)

No No DTC is displayed:
  • Go to the next step.
3 VERIFY IF MALFUNCTION CAUSE IS OVERHEATING 
  • Is the engine overheating?
Yes Go to the symptom troubleshooting "NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING".
(See NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING .)
No Go to the next step.
4 VISUALLY INSPECT THROTTLE BODY 
Yes Clean the throttle valve.
No Go to the next step.
5 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.
  • Access the following PCM PIDs using the M-MDS:

    (See ON-BOARD DIAGNOSTIC TEST .)

    • APP1
    • APP2
    • RPM
    • VPWR
    • MAF
    • TP1
    • TP2
    • VSS
  • Monitor each PID while driving the vehicle.
  • Are all PIDs normal?

    (See PCM INSPECTION .)

Yes Go to the next step.
No APP1 or APP2 PID is not specified:
  • Inspect if output signal from APP sensor changes smoothly.

RPM PID is not specified:
  • Inspect the CKP sensor and related wiring harness for vibration or intermittent open/short circuit.

VPWR PID is not specified:
  • Inspect for open circuit intermittently.

MAF PID is not specified:
  • Inspect for open circuit of the MAF sensor and related wiring harness intermittently.

TP1 or TP2 PID is not specified:
  • Inspect if output signal from TP sensor changes smoothly.

VSS PID is not specified:
  • Inspect for open circuit of VSS and related wiring harness intermittently.

Repair or replace the malfunctioning part according to the inspection results.
6 INSPECT CKP SENSOR 
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
7 VERIFY SPARK PLUG CONDITION 
  • Verify the spark plug conditions.
  • Is spark plug wet, covered with carbon or grayish white?
Yes Spark plug is wet or covered with carbon:
  • Inspect for fuel leakage from fuel injector.

Spark plug is grayish white:
  • Inspect the fuel injector for clogging.

Repair or replace the malfunctioning part according to the inspection results.
No Install the spark plugs on original cylinders.
Go to the next step.
8 INSPECT DRIVE-BY-WIRE CONTROL SYSTEM OPERATION 
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
9 INSPECT DEFORMED IN EXHAUST SYSTEM 
  • Visually inspect the exhaust system part.
  • Is there any deformed exhaust system part?
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
10 INSPECT FUEL LINE PRESSURE 
  • Install the fuel pressure gauge between the fuel pipe and fuel distributor.
  • Measure the fuel line pressure.

    (See FUEL LINE PRESSURE INSPECTION .)

  • Is the fuel line pressure correct?
Yes Go to the next step.
No Zero or low:
  • Inspect for the following:
    • Fuel pump relay
    • Fuel pump circuit
    • Fuel line for clogging

High:
11 INSPECT FUEL SYSTEM FOR FUEL LEAKAGE 
  • Visually inspect for fuel leakage at fuel injector O-ring and fuel line.
  • Service if necessary.
  • Is the fuel line pressure held after ignition is switched to off?

    (See FUEL LINE PRESSURE INSPECTION .)

Yes Go to the next step.
No Inspect the fuel injector.
(See FUEL INJECTOR INSPECTION .)
12 DETERMINE IF MALFUNCTION CAUSE IS A/C SYSTEM OR OTHER 
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 the pressure gauge to A/C low and high pressure side lines.
  • Start the engine and idle it.
  • Turn the A/C switch on.
  • Measure low side and high side pressures.

    (See REFRIGERANT PRESSURE CHECK .)

  • Are pressures within specifications?
Yes Go to the next step.
No If the A/C is always on:

For other symptoms:
  • Inspect the following:
    • Refrigerant charging amount
    • Condenser fan operation
  • Repair or replace the malfunctioning part according to the inspection results.
13 INSPECT CRUISE CONTROL SYSTEM 
NOTE:
  • The following test should be performed for symptom with cruise control ON. If other symptoms exist, go to the next step.
  • Inspect the cruise control system operation.
  • Is the cruise control system normal?
Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
14 INSPECT CURRENT A/F SENSOR SIGNAL 
Yes Inspect the A/F sensor installation and exhaust gas leakage.
Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
15 INSPECT PCV VALVE 
NOTE:
  • The PCV valve cannot be reassembled once it is removed because the tabs will have been broken. Inspect the PCV valve without removing it from the vehicle.
  • Inspect the PCV valve with it installed.

    (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION .)

  • Is there any malfunction?
Yes Replace the PCV valve.
(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION .)
No Go to the next step.
16 DETERMINE IF MALFUNCTION CAUSE IS CHECK VALVE (TWO-WAY) OR OTHER 
  • Inspect the evaporative purge hose between the fuel tank and the purge valve.
  • Does fuel flow into evaporative purge hose?
Yes Inspect the check valve (two-way).
(See FUEL TANK INSPECTION .)
Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
17 DETERMINE IF MALFUNCTION CAUSE IS EVAP CONTROL SYSTEM OR OTHER 
CAUTION:
  • While performing this step, always operate the vehicle in a safe and lawful manner.
  • Disconnect the vacuum hose between purge solenoid valve and intake manifold from purge solenoid side.
  • Plug opening end of vacuum hose.
  • Drive the vehicle.
  • Does the engine condition improve?
Yes Inspect the following:
  • Purge solenoid valve is stuck open.
  • EVAP control system

Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
18 INSPECT CMP SENSOR 
Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
19 INSPECT IF MALFUNCTION CAUSE IS LOW ENGINE COMPRESSION OR OTHER 
  • Is the engine compression correct?
Yes Inspect the following:
  • Valve timing
  • Internal transaxle part
  • Engine mounts
  • Check valve (two-way)

Repair or replace the malfunctioning part according to the inspection results.
No Inspect for cause.
Repair or replace the malfunctioning part according to the inspection results.
20 Verify test results.
  • If normal, return to diagnostic index to service any additional symptoms.

    (See SYMPTOM DIAGNOSTIC INDEX .)

  • 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.