Mazda 626 - Fast Idle;Runs on; Low Idle;Stalls During Deceleration

TROUBLESHOOTING
NO.8 FAST IDLE/RUNS ON
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 leakage from intake-air system
• Throttle body malfunction
Diagnostic procedure
STEP INSPECTION RESULTS
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 (234 “F) and
82°C (180‘ F) ?
Yes Go to next step.
No
ECT PID is higher than 112°C (234°F) :
Go to symptom troubleshooting No.16 "Cooling
system concerns - Overheating”.
ECT PID is less than 82'C (180'F) :
Go to symptom troubleshooting No.17 “Cooling
system concerns - Runs cold”.
2
Connect NGS tester to DLC.
Turn ignition switch on.
Retrieve any DTC.
Is any DTC displayed?
Yes DTC is displayed:
Go to appropriate DTC test.
No
No DTC is 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 cable free play.
4
Verify test results. If okay, return to diagnostic index to service any additional symptoms.
NO.9 LOW IDLE/STALLS DURING DECELERATION
9
Low idle/stalls during deceleration
DESCRIPTION • Engine stops unexpectedly at beginning of deceleration or recovery from deceleration.
POSSIBLE
CAUSE
• Vacuum leakage
• IAC valve malfunction
• Air leakage from intake-air system
• MAF sensor or related circuit malfunction
• TP sensor or related circuit malfunction
• Brake switch or related circuit malfunction
• Neutral/clutch switch or related circuit malfunction
Diagnostic Procedure
STEP INSPECTION RESULTS
ACTION
1
Does engine idle rough?
Yes Go to symptom troubleshooting No.7 for “Engine
runs rough / Rolling idle”.
No Go to next step.
2 Verify following:
• Proper routing and no damage of vacuum
lines
• IAC valve is connected properly.
• No air leakage from intake-air system
Are all items okay?
Yes
Go to next step.
No Service as necessary.
Repeat Step 2.
3
Connect NGS tester to DLC.
Turn ignition switch on.
Retrieve any DTC.
Is any DTC displayed?
Yes DTC is displayed:
Go to appropriate DTC test.
No
No DTC Is displayed:
Go to next step.
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