This could simply be a case of the engine’s idle speed being set too low. If that’s the case, even though it’s firing on all four cylinders, it can feel rough and lumpy as though there’s something major wrong. Then, as you increase the revs, the engine smooths out and feels normal again. Even a worn or broken engine mount can amplify vibrations at idle, as can an exhaust leak.

A good mechanic will be able to tell you quickly whether this is the case or if, in fact, the engine really is dropping a cylinder at idle. If the latter is the case, you may have a dud spark plug, ignition wire, sensor or even a blocked or dirty fuel filter. Again, most mechanics won’t have a problem tracking this one down.

The fact that the scan doesn’t throw up a fault code could be an indication that it’s something pretty fundamental at fault here. Have you checked the car’s earth points and the tightness and cleanliness of the battery terminals? Apparently simple things like this can easily cause a random misfire. How is the condition of the battery and the charging rate? Modern engines hate low operating voltages.

But don’t rule out a problem with the fuel system, either. You might have a faulty fuel pump or a dirty fuel filter or even a dud injector that’s causing the glitch. Don’t forget to check the wiring to these components, either as a simple loose wire could be the problem.

If you do need to dig deeper, you could try checking the engine’s compression and the clearances of the engine valves. Even something like a cracked cylinder head or faulty head gasket can cause a misfire that shows up at, say, a particular engine temperature, but not at other times.

The answer to this will depend on exactly which model Barina you have. In some models (typically earlier ones) the code is simply a servicing reminder to make sure the owner knows maintenance is due.

But in some versions of the Barina of this era, fault code 89 usually relates to a problem with the car’s thermostat. So don’t drive it any farther as the faulty thermostat could cause the engine to overheat with catastrophic results. Have a mechanic check things out and see if the thermostat is indeed faulty. If it is, it’s a relatively cheap fix, certainly compared with the cost of a new engine.

Sometimes the code relates to a switch in the thermostat that is responsible for switching on the car’s electric fans, but either way, it could lead to overheating. Don’t ignore it in any case.