Nissan Sedan Range

Actually, it’s none of those things. This model Pulsar came with the option of a six-speed manual. But if it was an automatic Pulsar, it was fitted not with a conventional automatic, but with a CVT or Constantly Variable Transmission. Instead of a series of gears inside it, the CVT uses cones of different diameters linked by a flexible belt. By altering where on the cones the belt rides, the gearbox can produce different 'gears'.

The idea is that by providing an infinite number of ratios, the engine can always run closer to its most efficient speed, therefore improving fuel efficiency. It’s a great theory, but not all drivers like the sound and feel of a CVT which can feel pretty alien, especially at first. Some manufacturers, in an attempt to make the CVT feel more familiar, electronically engineer in fixed `ratios’ but, in reality, this removes some of the CVT’s efficiency-boosting potential.

I take it the smoke is coming out the tailpipe when you crank the engine, even though the engine is not starting or, at least, not running to the point where the car can be driven. It sounds like you might have 'cooked' the engine as old school mechanics would put it. When the radiator started leaking, allowing the coolant to escape, the engine overheated and 'cooked'. Which means the severe heat inside the engine damaged something sufficiently that the engine now won’t run.

You could be dealing with a blown head gasket or a warped cylinder head, or even damage to the pistons. The smoke you’re seeing when you crank the engine could be oil smoke that’s a result of fired piston rings due to the overheating episode. The first thing to do is let a mechanic run a few tests on the engine to determine whether it’s retrievable or junk. From there, you can make an informed decision on whether to fix the car or cut your losses and simply walk away. If the engine is damaged beyond help, a second-hand engine from a wrecked Tiida might be an option if you decide you want to keep the car.

Modern engines rely on a raft of sensors to inform the computer of what’s going on under the bonnet and what needs to be adjusted to keep the thing running smoothly and efficiently. A car that is using too much fuel and stalling could be having a problem with the sensor that tells the on-board computer that the engine is up to operating temperature. A cold engine needs more fuel to run properly so, if the sensor is telling the computer that the engine is still cold, the computer will continue to inject extra fuel into it. Of course, if the engine is up to temperature (regardless of what the sensor says) that extra fuel will show up as increased fuel consumption and could easily make the engine stall or run roughly.

However, that’s just one possibility and with the dozens of sensors dotted around a modern engine, the best advice is to have the car electronically scanned to see what fault codes are thrown up. The good news is that these sensors are usually inexpensive to replace and should return things to spot on pretty much immediately. Other suspects would be oxygen sensors and maybe even the stepper motor which controls the idle speed.