Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL FS]
STEP
INSPECTION
ACTION
3
Is engine overheating? Yes
Go to flowchart 17 for “COOLING SYSTEM CONCERNS
OVERHEATING”.
No Go to next step.
4
Connect NGS tester to DLC.
Access RPM PID, VPWR PID, VREF PID,
MAF PID, TP V PID, and VSS PID.
Drive vehicle with monitoring PIDs.
• VPWR PID: Battery voltage.
• PRM PID: Idle speed at idle.
• MAF PID.
c r 0 1 -4 0 A MASS AIR FLOW SENSOR
INSPECTION [FS]
• TP V PID.
c r 01—40A THROTTLE POSITION
SENSOR INSPECTION [FS]
• VSS PID.
zr
0 5 -17A VEHICLE SPEED SENSOR
INSPECTION [LA4A-EL]
Are PIDs within specification?
Yes
Go to next step.
No
RPM PID:
Check crankshaft position (CKP) sensor and related
harness; such as vibration, intermittent open/short circuit.
VPWR PID/VREF PID:
Check for open circuit intermittently.
MAF PID:
Check for open circuit of mass air flow sensor and related
wire harness intermittently.
TP V PID:
Check if output signal from throttle sensor changes
smoothly.
VSS PID:
Check for open circuit of vehicle speed sensor and related
wire harness intermittently.
5 Visually inspect crankshaft position (CKP)
sensor and teeth of crankshaft pulley.
Is CKP sensor and teeth of crankshaft pulley
okay?
Yes
Go to next step.
No Replace malfunctioning part.
6
Measure gap between crankshaft position
(CKP) sensor and teeth of crankshaft pulley.
Specification
0.5— 1.5 mm {0.02— 0.05 in}
Is gap within specifications?
Yes Go to next step.
No Adjust CKP sensor.
7 Check spark plug conditions.
Is spark plug wet, converted with carbon or
grayish white?
Yes If spark plug is wet or converted with carbon, check for
fuel leak from fuel injector.
If spark plug is grayish white, check for clogged fuel
injector.
No Install spark plugs on original cylinders.
Go to next step.
8
Remove PCV valve and shake PCV valve.
Does PCV valve rattle? Yes Go to next step.
No Replace PCV valve.
9 Check that throttle lever is resting on throttle
valve stop screw and/or throttle valve orifice
plug.
Is lever in correct position?
Yes Go to next step.
No Adjust as necessary.
1 0
Are there restrictions in the exhaust system? Yes Check exhaust system.
No Go to next step.
1 1
Install fuel gauge between fuel filter and fuel
distributor. Connect NGS tester to DLC.
Select “ALL ON” in OUTPUT TEST MODE
and press start.
Is fuel line pressure correct with ignition switch
ON?
Fuel line pressure
260— 310kP a
{2.6— 3.2 kgf/cm2, 37— 46 psi>
Yes Go to next step.
No
Zero or low:
Check fuel pump circuit.
Check for open fuel pump relief valve.
Check for fuel leak inside pressure regulator.
Check for clogged main fuel line.
H igh:
Check pressure regulator for high pressure cause.
Check for clogged fuel return line.
1 2
Visually check for fuel leakage at fuel injector
O-ring, pressure regulator, and fuel line.
Service as necessary.
Does fuel line pressure hold after ignition
switch is turned off?
Fuel line pressure
More than 150 kPa
{1.5 kgf/cm2, 21 psi} for 5 minutes
Yes Go to next step.
No Check pressure regulator diaphragm condition.
If condition is okay, check fuel injector.
If condition is not okay, replace pressure regulator.
0 1 -0 1 A - 1 44