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.

It sounds like the new head gasket isn’t working properly and the car is still overheating. Or, the root problem wasn’t the head gasket in the first place, or that the mechanic missed something crucial that allowed the new head gasket to fail almost straight away.

Was the cylinder head checked for straightness? Was the cylinder block checked for cracks? A warped cylinder head or cracked block or bore can give symptoms just like a failed head gasket, but replacing the gasket won’t fix them. I think you need to have a deep and meaningful conversation with your mechanic and work out a plan to either dig further into the engine or replace it with a second-hand unit that’s been tested. The latter is probably the smarter, cheaper way to go. Either way, though, you risk spending more on the car than it’s actually worth. Maybe it’s time for something newer, more efficient and safer, not to mention more reliable.

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.