Ford Focus running rough

A Ford Focus 1.8 TDCi was brought to our facility experiencing rough running conditions.
The owner reported that the vehicle had been serviced recently, which raised questions about the maintenance history.
During a diagnostic test drive, we noted a significant power deficit within the 1,000 to 3,000 rpm range, followed by a gradual power increase.
We also discovered that the air filter was clogged, which could contribute to the poor performance at lower RPMs.
Additionally, the temperature gauge failed to exceed 70°C, prompting a return to our workshop for further investigation.
Further testing revealed that the thermostat was stuck open, which could impede the engine’s ability to reach optimal operating temperatures.
Upon examining the vehicle, we confirmed that while coolant levels were sufficient, the radiator hose was excessively pressurized, signaling a potential head gasket failure.
This finding warranted a more in-depth analysis of the engine’s internal components to ensure no further damage had occurred.
After allowing the engine to cool, we removed the radiator cap and conducted a sniff test, which validated our initial concerns.
After confirming the head gasket issue, we also checked the condition of the oil for signs of coolant contamination.
We then proceeded with the necessary head gasket repairs, restoring proper functionality to the cooling system.
This step was crucial to prevent any recurrence of similar problems in the future.

Following the completion of repairs, we allowed the engine to reach its normal operating temperature before conducting another test drive; however, we still observed a deficiency in low-end power.
Despite the initial repairs, it became clear that additional tuning was necessary to fully restore the vehicle’s performance.
Conversely, the vehicle performed admirably above 3,000 rpm, leading us to deduce that the car’s engine management map was suboptimal for road use.
Consequently, we implemented the new map after discussing the options for optimizing the fuel mixture and ignition timing.
We utilized AlientTech to remap the engine with our stage 1 tuned files, resulting in an impressive gain of 30 bhp and 70 Nm of torque compared to the standard stock file.
This tuning not only improved performance but also enhanced overall fuel efficiency, leading to a more enjoyable driving experience.
This upgrade ensured the vehicle now operates smoothly with consistent power delivery across the rev range, while maintaining engine integrity.