This version of the Ford 5.4-litre V8 is not universally admired by mechanics. It can tend to run hot, and it’s quite common for this unit to suffer from stretched timing chains, worn chain tensioners and guides. Any problem in the area of the timing chains can lead to a misfire or stumble, and it can be worse when the engine is hot and the oil pressure that powers the timing chain mechanisms starts to fall away.

The best advice is to have the car electronically scanned. This might pinpoint the problem by throwing up a fault code that a mechanic can decipher (including the camshaft timing fault we’re talking about). Don’t continue to throw new parts at the engine; that’s a great way to waste time and money and still not fix the problem.

When you say you have fuel, spark and air. How sure are you? These are not complicated engines and given all three of those things are present, the thing is kind of obliged to run. For instance, while you might be able to hear the fuel pump running (suggesting that fuel is being supplied) have you checked the fuel volume and pressure at the injector rail? Similarly, while there may be power at the coil packs, are the spark plugs actually doing their job?

Beyond that, you need to start looking for an alternative problem and, in engines like this one, you’d probably start with things like the crank-angle sensor which supplies information to the computer to allow the engine to fire. If this – or any other – sensor is dodgy, it can put a stop to play. An electronic scan might reveal more clues.

A misfire under load is often suggestive of an ignition or fuelling fault. You can check the performance of the fuel pump to see that it's delivering the volume of fuel it should, but don't ignore things like dirty fuel filters as a cause of poor fuel delivery.

That said, this engine is particularly susceptible to failures of the ignition coils. In fact, most mechanics who know their way around this engine will suspect faulty coils before anything else. It's not a terribly expensive fix even though there is a separate coil for each cylinder, but nine times out of ten, this will be the problem in a misfiring Falcon or Fairmont. The other piece of advice is to ensure you only use the genuine Ford ignition coils rather than a cheaper, knock-off coil.