If your engine idle speed is unusually high, it means the engine is running faster than normal when the car is stopped. This can waste fuel, increase wear, and make driving uncomfortable. High idle speed usually points to issues with the air intake system, sensors, or idle control components that regulate engine speed.

What does it mean if the engine idle speed is high?

A high idle means the engine is receiving too much air, fuel, or both when it should be idling at a steady, low RPM. Modern cars use sensors and the ECU to control idle speed, so a fault in these systems often triggers the problem.

Common causes of high idle speed

• Faulty idle air control valve (IACV)
• Vacuum leaks in hoses or intake manifold
• Sticking throttle body or throttle plate
• Faulty mass airflow (MAF) or throttle position sensor (TPS)
• ECU or engine control software issues
• Incorrectly adjusted or damaged accelerator cable (older cars)

Why do you need to fix this problem quickly?

Running at high idle wastes fuel, increases emissions, and puts extra strain on the engine and transmission. In severe cases, it may also make gear engagement jerky or unsafe.

How do you know when to get it checked?

You should book an inspection if:

• The engine revs higher than usual when stopped or in neutral
• The idle speed fluctuates or surges on its own
• The Check Engine Light is illuminated
• You hear hissing noises (possible vacuum leak)
• Fuel economy has dropped unexpectedly

What happens during an assessment?

A mechanic will:

1. Check the idle speed against manufacturer specifications
2. Scan the ECU for fault codes
3. Inspect for vacuum leaks in hoses and intake system
4. Test the idle air control valve, MAF, and TPS sensors
5. Clean or adjust the throttle body if required
6. Advise on necessary repairs or replacements

How much does it cost to fix?

Vacuum leak repairs or throttle body cleaning typically cost $120–$250. Idle control valve or sensor replacements usually range from $250–$600. More complex ECU or wiring faults may cost $700–$1,200+.

Is it unsafe to drive with high idle speed?

Yes. High idle speed can make the car harder to control at low speeds, increase stopping distances, and accelerate wear on drivetrain components. It should be inspected and repaired promptly.