What Is Start-Stop System (Eco-Idle) and How Does it Work?

Before we begin, it’s necessary to understand, what car idling and eco idling mean. A car is said to be in “car idling” state when it’s not in motion and the engine is still running. This means that when you are waiting in a car, and the engine is running, your car is in car idling state.

Car Idling is somewhat harmful because the exhaust of the car still releases emissions. Car idling is in short, harmful for both, health and the climate. A lot of people often believe that car idling can save fuel, this however is wrong. Keeping a car idle for a long period can waste a lot of fuel. Another misconception is that people recommend warming a car up by keeping the engine idle, this is not true, the best way to warm up a car is to drive it without revving the engine too much. When an engine is at optimum temperature, starting and stopping it does not use excessive fuel. That’s where the concept of start-stop system comes in.


Start-stop system automatically limits idling in a motionless vehicle. The start-stop system is also known as stop-start system. Volkswagen introduced its first production stop-start system in 1983 with the Polo Formel E.

In start-stop system, when the car comes to a stop, the engine stops the spark plug and fuel. When the driver lifts his foot off the brake, or presses the clutch, the engine automatically fires up. A car with start-stop system must have a strong starter motor, so that it can withstand the on-off cycle of the car. A good battery with enough amperes is also required, in order to satisfy the car’s entire electrical needs, when the engine is off.

Eco Idle explained

Many Japanese cars that are being imported into Pakistan come with the start-stop system. These cars also have a pre-stop idle reduction function, which automatically stops the engine when the car is at 7km/h or less when brakes are applied. Even with the engine stopped, the car’s electrical systems like audio and navigation are still available for use. When the car is in start-stop mode, its AC goes to ventilation mode. When the brakes are released, the engine starts up instantly.

In 2008, Mazda tried to introduce a theoretical Smart Idle Stop System (SISS). The idea of this system was to make the engine start without relying on the starter motor. The idea behind SISS was to stop all four pistons in the engine halfway through their stroke. In order to restart the engine, a cylinder in its compression stroke would get a small squirt of fuel, which would cause just enough combustion to get the crank spinning. This system, however, didn’t get materialized. Mazda then designed the “i-stop” system.

(Video Courtesy: Johnson Controls)

The i-stop is a start-stop system, which doesn’t use the electric starter motor to re-fire the engine like most auto manufacturers do. Mazda instead designed the system in such a way that one cylinder stops at a point near the top of its stroke. The system then fires that particular cylinder to get the engine started once the driver releases the brakes. This system hasn’t received any positive response as it doesn’t have any effect on EPA fuel economy ratings.

A few cars that are imported into Pakistan with the start-stop system include Daihatsu Mira Eco Idle, Suzuki Wagon R and Suzuki Alto. The start-stop technology increases fuel efficiency by 4-7 kilometers of in-city driving.

Samiullah Sharief

Samiullah Sharief is a car enthusiat. He is passionate about writing blogs and reviews about cars. His hobbies are driving,watching TV Shows like Top Gear, Mega Factories and he follows Popular car magazines. You can reach out to him by tweeting @sami649

  • Adnan malik

    My query is in Pakistan Traffic Jam when it starts again and again within few secs less than a minute it cannot increase fuel consumption?What myth i believe is starting car again causes more fuel consumption.can you clear me on it.Thanks

  • German Ab

    in Pakistan traffic when car engine stop and starts again and agin within secs, can it weaken the engine, electric and other systems of 660 jdm car?

  • shahzaib qammmer

    Adnan malik question is Good.

    Its work in both Auto on and OF(user adjustable)

  • Saad Rehman

    salam wanna know if the idle stoping is available in nissan dayz 2014 L PACKAGE CAN ANYBODY TELL ME ND HOW TO FIND OUT ABOUT THAT

  • Muhammad Ali Khan

    “Another misconception is that people recommend warming a car up by keeping the engine idle, this is not true, the best way to warm up a car is to drive it without revving the engine too much.”
    Dear Samiullah, Can you please elaborate this point further. if we start the car in winter it shows cold sign on odometer. can you still run/drive the car or should wait for cold sign to go and then drive? Running cold engine right away doesnt harm the engine at all??? if it really doesnt, why the RPM of car is higher to make it warm quickly?

  • khawar Islam

    I have wagon r 2013 model, Vehicle Speedo meter indicate eco idling fault instantly. What is the cause behind this?

  • Inayat ullah

    Suzuki Alto the code is coming p1360 stop &Go (Eng A stop battery performance)

  • Saiyeed Mashkur Al – Hakim

    Can we install CNG kit in a car that has Smart Stop technology