What to do when the engine fails to idle

Some engines may fail to keep idling speed despite efforts to replace parts to do with idling.

Idling of an engine is vital to its operation. Idling is the speed at which the engine runs when the accelerator pedal is not depressed.  

In many cases, if a car has an idling problem, the engine will stop if the driver takes the foot off the accelerator pedal. Since some systems are only effective when the engine is running, the driver will find it hard to brake efficiently since the braking system uses vacuum generated from the running engine. 

The steering wheel will also be hard to steer, making manoeuvring the car very difficult. 

In a traffic jam, the driver has to keep starting the vehicle as the engine will keep going off whenever the car stops. This is not only annoying but also increases accident risks.

It divides the driver's concentration between maintaining road order and safety as well as trying to keep the engine running by stepping on the accelerator pedal. 

I met someone who almost sold her car because of an idling problem. 

Causes

Many mechanics focus on major causes and neglect the minor ones. 

Air throttle valve

The air throttle valve is a unit located between the engine and the air cleaner. It has a butterfly valve that regulates the flow of air into the engine. When the accelerator pedal is depressed, the valve choke moves and allows more air into the engine. 

When the accelerator pedal is not depressed, this valve is closed but it has a tiny gap that allows in just enough air to keep the engine running. 

If this valve is clogged and air does not flow, the engine cannot idle. Many mechanics start by replacing coils, plugs, fuel pump, air cleaner, plug wires or engine sensors. This will be futile because what the engine needs is air to run. 

Solution

The solution is to use petrol to clean the valve to reinstate the idling gap. Next time you have a defiant idling problem; start with checking the cleanliness of the air throttle valve.