It’s a bit hard to imagine how removing and replacing a transmission could make an engine misfire or backfire. Unless, that is, you’ve managed to bump part of the engine’s electronic controllers, wiring, sensors or even something as simple as pinched or displaced a vacuum line somewhere in the engine bay. Incorrect ignition timing can make an engine do this, but, again, that’s nothing to do with the transmission.

It could even be a complete coincidence. But did the vehicle sit for any length of time while the transmission was being fixed? You might find the battery has discharged over time. Modern, electronically-controlled engines do not like low battery voltage and can run poorly as a result.

There are plenty of things that can cause this, but being a petrol engine with no turbocharger, it shouldn’t be too tricky to diagnose. Any time an engine runs well when warm but struggles when cold, suspicions are drawn to the fuel/air mixture. A warm engine needs a very different mixture to a cold engine, so modern engines have sensors that monitor the engine temperature, the air/fuel ratio and how well that mixture is burning. If any of those sensors are not telling the computer everything it needs to know, poor running can be the result.

But it would also be worth looking at the air intake side of things. An air or vacuum leak into the intake manifold can also cause rough running and hard starting. The engine’s stepper motor (which controls the idle speed) could also be at fault, but could also be the victim of one of those non-working sensors.

On most cars, you can disable beeps and buzzers that tell you the car has locked or unlocked. Many people choose to do so, too, out of consideration for their neighbours who don’t appreciate even a small toot of a car’s horn when you leave for work at 5am.

On newer LDVs, you can go to the touchscreen and hit Settings. Then touch 'Car' and then 'Comfort' and 'Convenience'. That will then offer a list of features, but the one you want to touch on is 'Locking Feedback'. That will then give you the choice of 'Lights and Horn', 'Lights Only' or 'Horn Only'. By touching on 'Lights Only', you should have disabled the horn beep when locking and unlocking. Your neighbours will thank you.