Mondeo Mk4 Ecoboost: a major engine service

28 February 2023 - Reading time: 2 minutes

As part of preventive maintenance, last month I performed a serious engine service, which included:

• Replacing the timing chain
• Cleaning the cylinder head (direct injection engines tend to have very dirty intake valves)
• Replacing piston rings, seals, gaskets, injectors, spark plugs, lambda sensors, PCV valve, and MAP sensor<
• Repairing the injection pump (the lifter showed some wear)

Inside, the engine is in surprisingly good shape - fairly clean and with minimal varnish build-up, a sign of timely maintenance. A few accessory bolt threads were damaged, apparently from mechanics not used to working on aluminum engine blocks, so I repaired the threads and installed original bolts.

The variable valve timing units were a bit unusual - a hybrid between the 2011 model and newer versions - and I had a fault code related to slow response on the intake cam. I replaced the units with the correct ones for this car, and the error cleared.

Since this overhaul, fuel consumption has dropped - though it’s hard to measure exactly - from about 14.4 L/100km in the city down to around 12.8. I’ve been driving the car during typical hours for several weeks, and it hasn’t risen above 12.8, so I’m confident this is a reasonable estimate. The engine runs much smoother and quieter, especially at idle, and some minor vibrations have disappeared. My impression is that the lambda sensors and injectors played a big role in reducing fuel consumption, but the cylinder head cleaning shouldn’t be overlooked either.