Mazda MX-6 1998, Workshop Manual

Page: 169 / 1282

TROUBLESHOOTING [ENGINE CONTROL FS]
STEP INSPECTION ACTION
13 Connect NGS tester to DLC.
Start engine and run it at idle.
Access LONGFT1 PID.
Measure LONGFT1 PID at idle.
Is PID value between 22------23%?
Yes Go to next step.
No LONGFT1 PID is out of specification.
Less than specification (too rich):
Check evaporative emission control system. If system is
okay, go to step 15.
Greater than specification (too lean):
Check for air leakage at intake air system components.
If system is okay, go to next step.
14 Disconnect vacuum hose between purge
solenoid valve and intake manifold from
solenoid side.
Plug open end of vacuum hose.
Start engine.
Does engine condition improve?
Yes Check if purge solenoid valve sticks open mechanically.
Check 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 a restriction in the exhaust system? Yes Check exhaust system.
No Go to next step.
17 Visually inspect camshaft position (CMP)
sensor and tooth of camshaft.
Is CMP sensor and tooth of camshaft okay?
Yes
Go to next step.
No Replace malfunctioning part.
18 Check the 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 Check valve timing.
No
Check for causes.
2 0
Verify test results. If okay, return to diagnostic index to service any additional symptoms.
8
FAST IDLE/RUNS ON
DESCRIPTION
• Engine speed continues at fast idle after warm-up
• Engine runs after ignition switch is turned off
POSSIBLE
CAUSE
• Engine coolant temperature malfunction
• Air leak from intake air system
• Throttle body malfunction
• Misadjustment of accelerator cable free play
• Misadjustment of cruise control cable
STEP
INSPECTION
ACTION
1
Connect NGS tester to DLC.
Access ECT PID.
Start and warm-up engine to normal operating
temperature.
Is ECT PID reading between 112 “ C {233.6
•F} and 82 ‘ C {179.6 °F}?
Yes
Go to next step.
No If ECT PID is higher than 112 "C {233.6 °F}:
Go to flow chart 17 for engine overheating.
If ECT PID is less than 82 X {179.6 °F):
Go to flow chart 18 for runs cold condition.
2
Retrieve and record any continuous memory,
KOEO and KOER DTCs.
Are there any DTCs displayed?
Yes Go to appropriate DTC test.
No No DTC displayed.
Go to next step.
3
Is there air leakage felt or heard at intake air
system components while racing engine to
higher speed?
Yes Repair or replace parts as necessary.
No
Verify accelerator and/or cruise control cable free play.
4
Verify test results. If okay, return to diagnostic index to service any additional symptoms.
01-01A-141