Torque Shop

Something strange happened while I was driving my three-month-old Mercedes-Benz C-class in a multi-storey carpark recently.

As the car went onto the ramp, there was a momentary loss of power, even though I was still accelerating. After a few seconds of hesitation, the car responded and continued up the ramp. The symptom resurfaced at the next ascending ramp.

I tried to induce the same symptom elsewhere, but I could not. The problem occurs only when I am turning and going uphill. Is this normal or is this a defect?

Like many cars these days, yours has a stability management system - generally known as electronic stability program (ESP).

It modulates power sent to the driving wheels based on traction available. Whenever impending slip is detected, the system will override the accelerator pedal input.

The system is also called dynamic stability control, active skid control or vehicle stability control - all of which function in the same manner to reduce chances of skidding.

What you have described is neither abnormal nor a defect. The C-class is rear-wheel-driven. When turning sharply onto an ascending ramp, the car is at a diagonal pitch, causing two wheels to be less laden. One rear wheel will therefore tend to slip, prompting the ESP to curtail power. The momentary loss in power you experience is a result of a properly functioning system.

You can avoid the situation by maintaining a gentle throttle as you drive up the ramp or by switching off the ESP during the duration you are negotiating the ramps.

Under all other normal driving conditions, the system should never be switched off for safety reasons.

Shreejit Changaroth

A version of this article appeared in the print edition of The Straits Times on December 01, 2018, with the headline 'Torque Shop'. Print Edition | Subscribe