Mazda 6 2002, Workshop Manual

Page: 329 / 1248

TROUBLESHOOTING
F–199
F
NO.8 ENGINE RUNS ROUGH/ROLLING IDLE
A6E398018881W10
Diagnostic procedure
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
•
Air leakage from intake-air system parts
•
A/C system operation is improper
•
Spark leakage from high-tension leads
•
Spark plug malfunction
•
Purge solenoid valve malfunction
•
IAC valve improper operation
•
EGR valve malfunction
•
Erratic or no signal from CMP sensor
•
Low engine compression
•
Improper valve timing
•
Improper variable valve timing control system operation (L3-VE)
•
Erratic signal from CKP sensor
•
Poor fuel quality
•
PCV valve malfunction
•
Air cleaner restriction
•
Restriction in exhaust system
•
Disconnected electrical connectors
•
Inadequate fuel pressure
•
Fuel pump body mechanical malfunction
•
Improper load signal input
•
Fuel line restriction or clogging
•
Improper fuel injection control operation
•
Fuel leakage from fuel injector
•
Fuel injector clogging
•
Engine overheating
•
Vacuum leakage
•
Pressure regurator malfunction
Warning
The following troubleshooting flow chart contains fuel system diagnosis and repair
procedures. Read 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 injuries or
death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete
“BEFORE REPAIR PROCEDURE” and “AFTER REPAIR PROCEDURE” described in this
manual.
(See
F–17 BEFORE REPAIR PROCEDURE .)
(See F–17 AFTER REPAIR PROCEDURE .)
Caution
•
Disconnecting/connecting quick release connector without cleaning it may possibly 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.
STEP INSPECTION RESULTS ACTION
1 Verify following:
•
External fuel shut off or accessory (kill
switch, alarm etc.)
•
Fuel quality (e.g. proper octane,
contamination, winter/summer blend)
•
No air leakage from intake-air system
•
Proper sealing of intake manifold and
components attached to intake manifold:
EGR valve, IAC valve
•
Ignition wiring
•
Electrical connections
•
Fuses
•
Smooth operation of throttle valve
Are all items okay?
Yes Go to next step.
No Service as necessary.
Repeat Step 1.