Torque Shop

My Chevrolet Spark takes about two minutes in the morning for its engine to run normally. Why is this so?

A cold engine is never at its optimum because its design parameters are based on "normal operating temperature".

For most internal combustion engines, the only measure of normal operating temperature is the water temperature gauge. Some gauges only indicate "N" (for normal) - or, more commonly, just a mark in the middle of the temperature scale - while others show an analogue or digital figure of 90 deg C as the normal running temperature.

Any indication above this suggests the car is overheating.

Old carburetted engines used to take some time to reach normal running temperature. These cars have a manual or sometimes automatic "choke" to supply a slightly rich mixture when the engine is cold to alleviate rough performance during the warm-up period.

But with fuel-injected cars, the electronic controls will accurately manage fuelling and ignition to deliver sufficiently smooth performance from cold starts.

A fuel-injected engine that runs erratically when cold suggests an ignition or fuel-injection fault.

If your fuel-injected car takes two minutes to begin running smoothly, you should have a workshop run an electronic diagnosis to determine the fault and have it rectified as soon as possible.

Whether carburetted or electronically fuel-injected, always bear in mind that a cold engine should not be revved hard.

Shreejit Changaroth

A version of this article appeared in the print edition of The Straits Times on August 18, 2018, with the headline 'Torque Shop'. Print Edition | Subscribe