Mazda CX 7. Manual — part 89

SYMPTOM TROUBLESHOOTING [L3 WITH TC]

01-03–53

01-03

NO.14 POOR FUEL ECONOMY[L3 WITH TC]

id010339802000

14

POOR FUEL ECONOMY

DESCRIPTION

Fuel economy is unsatisfactory.

POSSIBLE CAUSE

• Contaminated air cleaner element

• Engine cooling system malfunction

• Improper ATF level

• Weak spark

• Spark plug malfunction

• Poor fuel quality

• Erratic signal from CKP sensor

• Erratic or no signal from CMP sensor

• Fuel pressure sensor or related circuit malfunction

• ECT sensor or related circuit malfunction

• Manifold absolute pressure (MAP) sensor or related circuit malfunction

• Accelerator position sensor or related circuit malfunction

• MAF sensor or related circuit malfunction

• Contaminated MAF sensor

• IAT sensor No.1 or related circuit malfunction

• IAT sensor No.2 or related circuit malfunction

• VSS or related circuit malfunction

• Variable swirl system malfunction

• Improper coolant level

• Inadequate fuel pressure (high-pressure side)

• Injection timing is incorrect

• Fuel injector or related circuit malfunction

• High pressure fuel pump malfunction

• Fuel leakage

• Fuel line restriction

• Fuel filter clogging

• PCV valve malfunction

• Brake dragging

• A/C system improper operation

• Improper valve timing due to jumping out of timing chain

• Improper engine compression

• Turbocharger malfunction

• Charge air cooler malfunction

• Exhaust system and/or three-way catalytic converter clogging

• EGR system malfunction

• Vacuum leakage

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 REPAIR ROCEDURE” and “AFTER REPAIR PROCEDURE” described in this
manual.
(See01-14-4 BEFORE REPAIR PROCEDURE[L3 WITH TC].)
(See01-14-4 AFTER REPAIR PROCEDURE[L3 WITH TC].)

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.

1871-1U-06B(01-03).fm 53 ページ ２００６年３月１５日 水曜日 午前１０時３６分

SYMPTOM TROUBLESHOOTING [L3 WITH TC]

01-03–54

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Inspect for the following:

• Air cleaner element for contamination

• Intake-air system restriction

• Fuel quality (proper octane, contamination,

winter/summer blend)

• Coolant level

• ATF level

• Brake dragging

• Charge air cooler condition (restriction or

damaged)

• Vacuum leakage

• Fuel leakage

• MAF sensor contaminated

• Exhaust system and/or three-way catalytic

converter restriction

Are all items normal?

Yes

Go to the next step.

No

Service if necessary.
Repeat Step 1.

2

Perform the self-test function using the M-MDS.
Turn the ignition switch to the ON position.
Retrieve any DTCs.
Is a DTC displayed?

Yes

DTC is displayed:
Go to the appropriate DTC test.
(See01-02-13 DTC TABLE[L3 WITH TC].)

No

No DTC is displayed:
Go to the next step.

3

Perform the Cooling Fan Control System
Operation Inspection.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Does the EGR system operate properly?

Yes

Go to the next step.

No

Inspect or replace the malfunctioning parts, according
to the inspection results.

4

Perform the EGR system operation inspection.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Does the EGR system operate properly?

Yes

Go to the next step.

No

Inspect or replace the malfunctioning parts, according
to the inspection results.

5

Perform the Variable Swirl Control System
Operation Inspection.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Does the variable swirl system work properly?

Yes

Go to the next step.

No

Inspect or replace the malfunctioning parts, according
to the inspection results.

6

Perform the Wastegate Control System
Operation Inspection.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Does the variable swirl system work properly?

Yes

Go to the next step.

No

Inspect or replace the malfunctioning parts, according
to the inspection results.

7

Perform the A/C Cut-off Operation Inspection.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Does the A/C Cut-off Operation work properly?

Yes

Go to the next step.

No

Repair or replace malfunctioning parts, according to
the inspection results.

8

Remove and shake the PCV valve.
Does the PCV valve rattle?

Yes

Go to the next step.

No

Replace the PCV valve.

9

Perform the spark test.
(See01-03-78 ENGINE CONTROL SYSTEM
OPERATION INSPECTION[L3 WITH TC].)
Is the strong blue spark visible at each cylinder?

Yes

Go to the next step.

No

Inspect or replace the malfunctioning parts, according
to the inspection results.

10

Inspect CMP and CKP sensor for the following;

• Installation condition

(See01-40-45 CAMSHAFT POSITION
(CMP) SENSOR REMOVAL/
INSTALLATION[L3 WITH TC].)
(See01-40-42 CRANKSHAFT POSITION
(CKP) SENSOR REMOVAL/
INSTALLATION[L3 WITH TC].)

• Damaged trigger wheel and camshaft

• Open or short circuit in the wiring harnesses

Is there any malfunction detected?

Yes

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

No

Go to the next step.

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SYMPTOM TROUBLESHOOTING [L3 WITH TC]

01-03–55

01-03

End Of Sie

11

Connect the M-MDS to the DLC-2.
Access and monitor following PIDs using the
data monitor function.

• ECT

• MAF

• IAT

• IAT2

• APP

• TP

• MAP

• VSS

Do the PIDs indicate the correct values
according to the engine operating condition?
(See01-40-6 PCM INSPECTION[L3 WITH TC].)

Yes

Go to the next step.

No

Inspect and repair or replace suspected parts and the
related harnesses.
If the malfunction remains, perform the intermittent
concern troubleshooting procedure.
(See01-03-76 INTERMITTENT CONCERN
TROUBLESHOOTING[L3 WITH TC].)

12

Access and monitor the FUEL_PRES PID.
Is the FUEL_PRES PID value within the
specification?
(See01-40-6 PCM INSPECTION[L3 WITH TC].)

Yes

Go to Step 16.

No

Go to the next step.

13

Is the vehicle accelerate performance normally?

Yes

Go to the next step.

No

Go to Step 15.

14

Inspect the fuel pressure sensor.
(See01-40-35 FUEL PRESSURE SENSOR
INSPECTION[L3 WITH TC].)
Is the fuel pressure sensor normal?

Yes

Go to Step 16.

No

Replace the delivery pipe.

15

Replace the high pressure fuel pump.
Monitor FUEL_PRES PID.
Is the FUEL_PRES PID value within the
specified?
(See01-40-6 PCM INSPECTION[L3 WITH TC].)

Yes

Troubleshooting is completed.
Go to Step 19.

No

Go to the next step.

16

Inspect the turbocharger.
(See01-13-17 TURBOCHARGER
INSPECTION[L3 WITH TC].)
Is there any problem in turbocharger?

Yes

Replace the turbocharger.

No

Go to the next step.

17

Inspect the fuel injector for each cylinder.
(See01-14-27 FUEL INJECTOR
INSPECTION[L3 WITH TC].)
Are fuel injectors normal?

Yes

Go to the next step.

No

Replace the suspected fuel injector.
(See01-14-23 FUEL INJECTOR REMOVAL/
INSTALLATION[L3 WITH TC].)

18

Measure the compression pressure for each
cylinder.
(See01-10-9 COMPRESSION INSPECTION[L3
WITH TC].)
Are compression pressures within the
specification?

Yes

Replace the injector driver module.
If the problem remains, overhaul the engine.

No

Inspect for the following:

• Damaged valve seat

• Worn valve stem and valve guide

• Worn or stuck piston ring

• Worn piston, piston ring or cylinder

• Improper valve timing

Service if necessary.

19

Verify test results.

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

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

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.

STEP

INSPECTION

RESULTS

ACTION

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SYMPTOM TROUBLESHOOTING [L3 WITH TC]

01-03–56

NO.15 EMISSION COMPLIANCE[L3 WITH TC]

id010339802100

15

EMISSION COMPLIANCE

DESCRIPTION

Fails emissions test.

POSSIBLE CAUSE

• Poor fuel quality

• Vacuum lines leakage or blockage

• Cooling system malfunction

• Engine overheating

• Spark plug malfunction

• Air leakage from intake-air system

• Variable swirl system malfunction

• Wastegate control system improper operation

• Turbocharger malfunction

• Charge air cooler malfunction

• Inadequate fuel pressure (high-pressure side)

• PCV valve malfunction or incorrect valve installation

• EGR system malfunction

• Exhaust system and/or three-way catalytic converter restriction

• Fuel tank ventilation system malfunction

• Charcoal canister damage

• Air cleaner element clogging or restriction

• Throttle body malfunction

• Improper operation of electronic throttle control system

• Relief valve malfunction (built-in delivery pipe)

• Suction control valve malfunction (built-in high pressure fuel pump)

• Improper air/fuel mixture ratio control operation

• Erratic or no signal from CMP sensor

• Erratic signal from CKP sensor

• Front or rear HO2S or related circuit malfunction

• ECT or related circuit malfunction

• MAF sensor or related circuit malfunction

• IAT sensor No.1 or related circuit malfunction

• IAT sensor No.2 or related circuit malfunction

• Fuel pressure sensor or related circuit malfunction

• Accelerator position sensor or related circuit malfunction

• TP sensor or related circuit malfunction

• Manifold absolute pressure (MAP) sensor or related circuit malfunction

• VSS or related circuit malfunction

• Fuel line restriction

• High pressure fuel pump malfunction

• Fuel injector or related circuit malfunction

• Incorrect fuel injection timing

• Three-way catalytic converter (TWC) malfunction

• Engine internal parts malfunction

• Excessive carbon is built-up in combustion chamber

• Improper engine compression

• Improper valve timing

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 REPAIR ROCEDURE” and “AFTER REPAIR PROCEDURE” described in this
manual.
(See01-14-4 BEFORE REPAIR PROCEDURE[L3 WITH TC].)
(See01-14-4 AFTER REPAIR PROCEDURE[L3 WITH TC].)

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.

1871-1U-06B(01-03).fm 56 ページ ２００６年３月１５日 水曜日 午前１０時３６分