Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1993 Volvo 850 L5-2.4L VIN 55 B5254SFACTORY OEM SERVICE PROCEDURE
High Idling Speed
HIGH IDLING SPEED
Conditions for Fault Tracing
^ No DTCs present.
^ Engine hot.
^ Fault is permanent.
Fault Sources:
^ Throttle cable sticking.
^ Throttle body (TB) incorrectly adjusted.
^ Air leakage.
^ Faulty Idle Air Control (IAC) Valve.
TESTING PROCEDURE
Checking Throttle Cable
^ Check that throttle cable is not sticking or moving sluggishly.
- Proceed to: Checking Throttle Opening.
Checking Throttle Opening
^ START engine and allow to idle.
^ Display and read throttle angle.
Throttle Angle should be 9 - 14° at Closed Throttle Position (CTP).
If angle is correct:
- Proceed to: Checking for Air Leakage.
If angle is incorrect:
- Adjust Throttle Body (TB) and throttle pulley.
Checking for Air Leakage
^ IDLE engine.
^ Display and read value of long term fuel trim at idling.
Value should be higher than -15.
If value is correct:
- Proceed to: Checking IAC Valve Connector.
If reading is less than -15:
- Check the air and vacuum hoses.
Checking IAC Valve Connector
^ Clean and grease MFI module and IAC valve connectors.
If symptoms persist:
- Try with new IAC valve.
Conditions for Fault Tracing
^ No DTCs present.
^ Engine hot.
^ Fault is permanent.
Fault Sources:
^ Throttle cable sticking.
^ Throttle body (TB) incorrectly adjusted.
^ Air leakage.
^ Faulty Idle Air Control (IAC) Valve.
TESTING PROCEDURE
Checking Throttle Cable
^ Check that throttle cable is not sticking or moving sluggishly.
- Proceed to: Checking Throttle Opening.
Checking Throttle Opening
^ START engine and allow to idle.
^ Display and read throttle angle.
Throttle Angle should be 9 - 14° at Closed Throttle Position (CTP).
If angle is correct:
- Proceed to: Checking for Air Leakage.
If angle is incorrect:
- Adjust Throttle Body (TB) and throttle pulley.
Checking for Air Leakage
^ IDLE engine.
^ Display and read value of long term fuel trim at idling.
Value should be higher than -15.
If value is correct:
- Proceed to: Checking IAC Valve Connector.
If reading is less than -15:
- Check the air and vacuum hoses.
Checking IAC Valve Connector
^ Clean and grease MFI module and IAC valve connectors.
If symptoms persist:
- Try with new IAC valve.
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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