Idle Air Control System Malfunction
What it means
The computer is trying to hold engine idle speed at a set target but cannot reach it. Most often the throttle body or idle air valve is coated with carbon, or there is a vacuum leak.
Symptoms4
- Idle speed too high or too low.
- Idle speed hunting up and down.
- Stalling at a stop or when the air conditioning switches on.
- Check engine light on.
Possible causes5
- Throttle body coated with carbon.
- Dirty or failed idle air control valve on cars that use one.
- Vacuum leak from a hose.
- Damaged connector or wiring on the valve or electronic throttle.
- Battery disconnection requiring an idle relearn.
How to diagnose and fix5
- Check for vacuum leaks and inspect hoses.
- Clean the throttle body and idle valve with a suitable cleaner.
- Perform the idle relearn procedure specified by the manufacturer.
- Inspect the valve or throttle connector and wiring.
- Replace the valve or throttle body if cleaning does not help.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
Cleaning is usually cheap, while an electronic throttle body can reach the second tier.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Frequently asked questions
I cleaned the throttle body and now the idle is odd. Why?
After cleaning, the computer often needs to relearn the idle position. Look up the relearn procedure for your car or use a scan tool that supports it.
Is stalling at idle dangerous?
It can be at junctions and roundabouts, because power steering assist is lost. Repair it as soon as possible.
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
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