Port cleaning

irect-injection is one of those ideas that probably seemed like a good idea at the time, and it was designed primarily for emissions. Rather than having the injectors in the manifold and operating under fairly low pressure with petrol carried into the cylinder with the intake air, the fuel is injected directly into the combustion chamber the other side of the inlet valve under very high pressure. That might seem a good idea but the on downside of this is that without the wet fuel in the intake charge, there is nothing to wash the intake ports or the backs of the valves. They shouldn’t get dirty but with the crankcase ventilation system recycling oil vapour into the intake charge a film of oil and recycled exhaust gas (EGR) builds-up. Some cars are absolutely terrible for this – the MINI is just one – and it’s possible that after 63,000 miles the inlet ports on our Renault-engined Qashqai could be pretty bad as well. As it turns out, they were in decent condition though with the manifold off – a simple