You’ve neglected to mention your car’s make and model, information that usually makes my task much simpler. Fortunately, all cars since 1996 share the basic codes: A P0303 is a misfire on cylinder No 3. Changing the plugs, wires and coils and cleaning the fuel injectors could have cleared that up. The new tyres and wheel balancing are unrelated to the unfriendly ghost, so athough it’s nice that you have fresh rubber, that’s not going to scare away the problem. (Please, stop me before I drive this metaphor into the ground!)

You – or actually, your workshop – seem to have been pretty thorough about looking for ignition and fuel-injection issues. So I’m thinking it’s time to turn your attention to mechanical issues, starting with a valve adjustment. Your car (whatever it is) may not call for periodic valve adjustments according to the codified maintenance schedule, but a tight valve could cause a recurrent misfire. While the cam cover is off, check for broken valve springs and worn valve guides. If everything appears in good order, do compression or leak-down tests. The compression readings among all the cylinders should be within 10 per cent, while the leakdown differentials should be within a couple of per cent (and certainly no more than 5 per cent) of each other.

If those tests don’t ferret out the issue, look for a bad exhaust gas recirculation (EGR) valve, especially if the EGR outlet into the manifold is anywhere near the intake runner to cylinder No 3. If the EGR is leaking exhaust into the manifold when it’s not supposed to, that may be the cause of the mysterious (spooky?) misfire. This last one is a long shot, because a bad EGR should set a code different to P0303.