Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL KL]
12 KNOCKING/PINGING - ACCELERATION/CRUISE
DESCRIPTION
Sound produced when air/fuel mixture is ignited by something other than spark plug (i.e., hot spot in
combustion chamber)
POSSIBLE
CAUSE
• Engine overheating due to cooling system malfunction
• Inadequate engine compression
• Inadequate fuel pressure
• Knock sensor and related circuit malfunction
Warning
Following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read
following warnings before performing fuel system service:
• 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 leaks 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.
tr 0 1 -1 4 BEFORE REPAIR PROCEDURE
a- 0 1 -1 4 AFTER REPAIR PROCEDURE
STEP
INSPECTION
ACTION
1 Connect NGS tester to DLC.
A r r o c c P O T P1I"”)
Verify ECT PID is less than 116 *C {240.8 °F}
during driving.
Is ECT PID less than specification?
Yes
Go to next step.
No Inspect cooling system for cause of overheating.
2 Retrieve and record any continuous memory,
KOEO and KOER DTCs.
Are there any DTCs displayed?
Yes
Go to appropriate DTC test.
No Go to next step.
3 Is engine compression correct? Yes Go to next step.
No Check for cause.
4 Install fuel pressure gauge between fuel filter
and fuel distributor.
Start engine and run at idle.
Measure fuel line pressure at idle.
Is fuel line pressure correct at idle?
Fuel line pressure
2 1 0 -2 6 0 kPa
{2.1— 2.6 kgf/cm2, 30— 37 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.
High:
Check pressure regulator for high pressure cause.
Check for clogged fuel return line.
5 Measure resistance between knock sensor
terminal and knock sensor body.
Specification
Approx. 560 k fi [20 °C {68 ’ F}]
Is resistance okay?
Yes Check ignition timing.
No Replace knock sensor.
6
Verify test results. If okay, return to diagnostic index to service any additional symptoms.
0 1 -0 1 B -1 54