If your engine shuts off when you slow down or stop, it usually means there’s a problem with idle control, fuel delivery, or airflow. While the car may restart, repeated stalling is unsafe and can damage engine components over time. Identifying the cause is essential to restore smooth idling and prevent breakdowns.

What does it mean if the engine shuts off when slowing down?

This typically indicates that the engine is not maintaining the correct idle speed. It could be caused by a faulty idle air control valve, dirty throttle body, vacuum leak, or issues with fuel supply or ignition timing.

Common causes of engine stalling at low speeds

• Faulty idle air control (IAC) valve
• Dirty or sticking throttle body
• Vacuum leaks in hoses or intake manifold
• Fuel delivery problems (clogged fuel filter or weak pump)
• Failing sensors such as MAF (mass airflow) or TPS (throttle position sensor)
• Ignition timing or spark issues

Why do you need to fix this problem quickly?

Stalling can leave you without power steering or braking assistance, creating a serious safety risk. It also makes the car unreliable and can worsen fuel efficiency or damage other components if ignored.

How do you know when to get it checked?

You should book an inspection if:

• The engine stalls when stopping at traffic lights or junctions
• Idle speed feels rough or unstable
• You notice poor fuel economy
• The Check Engine Light comes on
• The car struggles to restart after stalling

What happens during an assessment?

A mechanic will:

1. Scan the ECU for fault codes
2. Inspect and test the idle air control valve and throttle body
3. Check fuel pressure and filter condition
4. Inspect intake system for vacuum leaks
5. Test sensors such as MAF and TPS for correct operation
6. Confirm idle stability during a road test

How much does it cost to fix?

Costs depend on the cause. Cleaning a throttle body or IAC valve may cost $150–$300. Sensor replacements typically range from $200–$500. Fuel system repairs may cost $300–$900+.

Is it unsafe to drive if the engine stalls when stopping?

Yes. Stalling at low speeds or intersections can cause loss of control and increases the risk of accidents. The issue should be diagnosed and repaired immediately.