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2008 - MX-5 - Engine

NO.13 KNOCKING/PINGING-ACCELERATION/CRUISE [LF]



13

KNOCKING/PINGING - ACCELERATION/CRUISE

DESCRIPTION

Sound is heard when air/fuel mixture is ignited by something other than spark plug (such as hot spot in combustion chamber).

POSSIBLE CAUSE

  • Engine overheating due to cooling system malfunction

  • ECT sensor malfunction

  • IAT sensor malfunction

  • MAF sensor malfunction

  • Knock sensor malfunction

  • Erratic signal from CMP sensor

  • Inadequate engine compression

  • Inadequate fuel pressure

WARNING:

The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before servicing the fuel system:
  • 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 injuries 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 [LF].)

    (See AFTER SERVICE PRECAUTION [LF].)

CAUTION:

  • Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.


Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Connect the M-MDS to the DLC-2.

Access ECT PID.

Verify ECT PID is less than 116°C {241°F} during driving.

Is ECT PID less than specification?

Yes

Go to the next step.

No

Inspect the cooling system for cause of overheating.

2

Connect the M-MDS to the DLC-2.

Access IAT and MAF PIDs.

Monitor each PID.

(See PCM INSPECTION [LF].)

Are PIDs normal?

Yes

Go to the next step.

No

IAT PID: Inspect IAT sensor

MAF PID: Inspect MAF sensor

3

Connect the M-MDS to the DLC-2.

Turn the ignition switch to the ON position (engine off).

Are there any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC inspection.

(See DTC TABLE [LF].)

No

No DTC is displayed:

Go to the next step.

4

Is engine compression correct?

Yes

Go to the next step.

No

Inspect for cause.

5

Install fuel pressure gauge between fuel pipe and fuel distributor.

Start the engine and idle it.

Measure fuel line pressure during idle.

Is fuel line pressure correct during idle?

(See FUEL LINE PRESSURE INSPECTION [LF].)

Yes

Inspect the ignition timing.

No

Low:

Inspect the fuel pump relay and fuel pump circuit.

Inspect the fuel line for clogging.

If there is no malfunction, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [LF].)

High:

Replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [LF].)

6

Inspect the knock sensor.

Is the knock sensor normal?

Yes

Inspect ignition timing.

No

Replace the knock sensor.

7

  • Verify test results.

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

      (See SYMPTOM DIAGNOSTIC INDEX [LF].)

    • 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, replace the PCM.

        (See PCM REMOVAL/INSTALLATION [LF].)




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