ENGINE

EcoBoost, not EcoBust – the Focus ST’s turbocharged two-litre doesn’t have the same reputation for going pop as its 1.0 or 2.3 counterparts. Unfortunately, it also lacks the others’ impressive tunability.

Rather aptly, problems arise when an ST250’s output is increased too much – Gary at Collins Performance reckons standard engines hardly ever break, but over 300bhp is asking for trouble.

The most likely outcome will be piston failure, showing up as smoking, misfiring, running on three cylinders or knocking noises at idle. Don’t worry about a light tapping – the stock fuel injection clatters a bit anyway – but a heavier knocking means something is amiss.

A knackered piston will also result in loss of power; any ST250 should feel responsive from 2000rpm and effortlessly driveable. If not, walk away. The solution is a set of forged pitons and rods (with lowered compression ratio than the regular 10.0:1 if you plan on a big turbo and loads of boost) but they’re not cheap; on the plus side, they can be fitted with the engine in situ.

Be suspicious of white smoke from the exhaust, which could point to head gasket failure. It’s rare but not impossible, so check for coolant loss.

Blue smoke means oil is being burnt. A little at high revs could point to wear in the turbo – especially on a high-mileage or hard-worked car. Collins hasn’t yet had to replace a turbo, but the standard part is a little Borg-Warner K03, and it won’t last forever.

Smoking at idle is particularly common on STs fitted with decats, caused by oil blowing past the turbo seals thanks to excessive crankcase pressure and a somewhat unsophisticated breather system. Uprated breathers are available (the same part for ST and RS Focus models) but any smoke nevertheless needs deeper investigation.

Don’t be afraid to buy a modified Focus, because the ST250 responds exceptionally well to mild tuning – a remap, induction kit and sports exhaust not only awakens the performance but improves economy too.

Generally, the two-litre EcoBoost is ultrareliable, and issues rarely occur. Servicing is the same as any regular Ford, at every 12,500 miles; the engine uses a timing chain rather than belt, which means regular replacements aren’t required.

Perhaps the most likely problem you’ll find is bad idling, with revs fluctuating and the engine stalling, sometimes accompanied by a glowing management light. It’s caused by poor splicing in the underbonnet wiring loom – often referred to as a factory bodge – which on American STs resulted in an official recall. UK buyers weren’t so lucky – some had their whole wiring looms replaced, some were repaired in situ, and many others are yet to go wrong…