Mazda 626 Station Wagon, Workshop Manual

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TROUBLESHOOTING
STEP INSPECTION RESULTS ACTION
10 Start engine and disconnect IAC valve
connector.
Does rpm drop or engine stall? Yes Go to next step.
No Inspect IAC valve and wiring harness.
11
Install fuel pressure gauge between fuel main
pipe and fuel distributor.
Start engine and run it at idle.
Measure fuel line pressure at idle.
Is fuel line pressure correct at idle?
Fuel line pressure
210—260 kPa {2.1—2.6 kgf/cm2, 30—36 psi}
Yes Go to next step.
No Zero or low:
• Inspect fuel pump unit circuit
• Inspect for open fuel pump body relief valve
• Inspect for fuel leakage inside pressure
regulator
• Inspect for clogged main fuel line
• Inspect PRC solenoid valve, related vacuum
hose and harnesses
High:
• Inspect pressure regulator for high pressure
cause
• Inspect for clogged fuel return line
12 Visually inspect for fuel leakage at fuel injector,
O-ring, 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
min.
Yes Go to next step.
No Inspect pressure regulator diaphragm condition.
If condition is okay, inspect fuel injector.
If condition is not okay, replace pressure
regulator.
13 Connect NGS tester to DLC.
Start the engine and run it at idle.
Access FH02S or 02SII PID.
Is FH02S or 02SII PID okay?
• More than 0.45 V when accelerator pedal is
suddenly depressed: rich condition
• Less than 0.45 V during fuel cut: lean
condition
Yes Go to next step.
No Inspect and repair or replace faulty H02S,
harness, connector or terminal, then go to next
step.
14
Disconnect vacuum hose between purge
solenoid valve and intake manifold from purge
solenoid valve side. Plug opening end of
vacuum hose. Start engine.
Does engine condition improve?
Yes Inspect if purge solenoid valve is stuck open
mechanically.
Inspect evaporative emission control system.
No Go to next step.
15
Remove and shake PCV valve.
Does PCV valve rattle? Yes Go to next step.
No Replace PCV valve.
16 Is there restriction in exhaust system? Yes Inspect exhaust system.
No Go to next step.
17 Visually inspect CMP sensor and teeth of
camshaft.
Are CMP sensor and teeth of camshaft okay? Yes Go to next step.
No Replace malfunctioning parts.
18 Inspect engine condition while tapping EGR
valve housing. Does engine condition improve?
Yes Replace EGR valve.
No Go to next step.
19 Is engine compression correct? Yes Inspect valve timing.
No Inspect for causes.
20
Verify test results. If okay, return to diagnostic index to service any additional symptoms.
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