How to fix a car that stalls while idling?

By Julia Freeman

Many faults can cause a car to stall when waiting at traffic lights or coasting in slow traffic. Not all of them are serious but working out which is the cause can be difficult. Without some help you could find yourself dismantling and replacing a lot of parts before you fix the problem, so we highly recommend that you book a free vehicle check at a Protyre garage. In most cases, there is no charge until you decide to have a faulty component replaced. If the cause can’t be quickly established, we will recommend a diagnostic check using your on-board computer.

Car stalls while idling

A car engine needs three main things to function: fuel, air and electricity, so most causes of stalling boil down to one of these systems, although transmission issues can also be to blame. Here are few of the main suspects:

Fuel

Not many vehicles today have a manual choke, but they still need air and fuel in the right ratio. Checking the fuel filter is a good place to start. The fuel pump should also be checked and defective fuel injectors can also impede fuel delivery. These issues are more likely to cause a stall when stationary rather than at speed. If your car stalls after a run, when the engine is hot, there could be a cooling system issue.

Air

Leaky air hoses or gaskets can affect the air supply directly, or indirectly, by misleading the sensors that control it. If you have one, the mass airflow sensor (MAF) is a common culprit. It regulates how much air enters the engine: if the ratio is incorrect, the engine loses power and stops turning over. The idle air control actuator (IAC) can cause a similar problem.

Exhaust gases

Modern petrol and diesel engines recirculate some of the exhaust gases in order to reduce nitrogen oxide (NOx) emissions. If the exhaust gas recirculation valve (EGR) becomes stuck open, often because of soot, too much exhaust gas enters, reducing oxygen intake. This will usually result in fuel odours and poor mpg. Obstructions inside the muffler or catalytic converter can also cause a stall, a rotten egg smell usually means the converter need to be checked.

Other sensors and actuators

Sensors themselves can fail, or they can give false readings when there are faults in the hoses and components to which they are attached. The engine speed sensor, throttle position sensor (TPS), engine coolant sensor (ECT) and the crankshaft position sensor (CKP) can all cause an idle stall in some circumstances. Problems in the corresponding actuators have similar effects.

Electrics

Spark plugs are many motorists’ firstthought; plugs in poor condition can indeed cause low speed stalls but so too can faulty ignition coils, batteries, alternators, voltage regulators and loose wiring.

Transmission

If you drive an automatic, stalling can be caused by a torque converter problem or its solenoid, or by low transmission fluid.

The local garage you can trust

Our qualified fitters are experienced with all of these issues. Why not ask for a free tyre check at the same time? All Protyre garages carry a full range of tyres from Pirelli, Bridgestone, Continental, Dunlop, Falken, Avon and many other brands. It’s easy to book a free vehicle check through our website.

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About the author

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By Julia Freeman
Julia is Head of Retail Marketing for Protyre and loves engaging with customers and the business as a whole to make sure Protyre is more than just a local garage.
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