1.0 EcoBoost engine: faults and reliability

• 1.0 EcoBoost 100/125 (Fox, 2012-2017)

  2012–2017 · 100–125 hp · SFJA, SFJB, SFJC, SFJD

  With caution

  This is the version with the most documented cases of degradation of the belts running in oil and of coolant leak reports in early units; only recommended with the belts checked or replaced and no oil temperature or pressure warning lights.^[2][3][8]

• 1.0 EcoBoost 100/125/140 with cylinder deactivation (from ~2017)

  2017–2019 · 100–140 hp · M1JC, M1JJ, M1JU

  With caution

  Ford's 2023 recall in the US over the oil pump belt tensioner covers cars of this generation (Focus up to 2018 and EcoSport up to 2022), so the risk of seizure from this belt did not disappear with cylinder deactivation.^[9][10]

• 1.0 EcoBoost Hybrid 48V mild hybrid (125/155 hp, from 2019)

  since 2019 · 125–155 hp

  With caution

  This is the most recent version and has the best initial reputation, but we have not found a source confirming whether Ford changed the design of the belt running in oil in this particular variant; with fewer years on the road, the same precautions as for the earlier versions are advisable.^[1][11]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

1. 1Critical severityCommonFrequency: CommonTimingDegradation of the timing belt running in oilYes: the 1.0 EcoBoost's timing belt runs in oil and can degrade over the years, shedding bits of rubber that block the oil pump and seize the engine without warning. The NHTSA is investigating the case in the United States and Ford has shortened the recommended replacement interval.Repair (garage): €800–€1,200
2. 2Critical severityCommonFrequency: CommonLubricationOil pump belt and tensioner failureYes. In addition to the timing belt, the 1.0 EcoBoost has a second belt, also running in oil, that drives the oil pump. If the tensioner breaks, the belt loses teeth and can cut off oil pressure; in the US Ford has recalled more than 100,000 Ford Focus and EcoSport vehicles for this reason.
3. 3Critical severityOccasionalFrequency: OccasionalCoolingCoolant leaks and overheating from the turbo hoseThere are documented cases of turbo hoses that crack and drain the coolant without warning, which can overheat the engine and even seize it. We have not found a Ford campaign for the 1.0 EcoBoost in Spain; Ford's best-known fire recall concerns a different engine, the 1.6 EcoBoost.
4. 4Medium severityOccasionalFrequency: OccasionalIgnitionMisfires and engine warning light caused by the wiring harnessFord documented in a technical service bulletin that the engine wiring harness can rub against the exhaust heat shield on the 2018-2019 automatic EcoSport, which turns on the engine warning light with misfire fault codes. Spark plugs and coils are also common wear items on this turbocharged three-cylinder.

Severity colours: low, medium, high, critical. How we rate them

Manufacturer

Ford Motor Company

Family

EcoBoost (Fox)

Fuel

Petrol

Displacement

999 cm³

Cylinders

3

Fuel system

Turbo

Injection

Direct injection

Timing

Wet belt (belt-in-oil)

Power

100–155 hp

Peak torque

170 Nm

Production

since 2012

Makes

Ford

Technical data^[1][5][6][7]

1. 2012–2017

   1.0 EcoBoost 100/125 (Fox, 2012-2017)

   The Fox's launch version, with 100 and 125 hp. Both the timing belt and the oil pump belt run in oil, and the engine has no cylinder deactivation.^[1][13]

2. 2017–2019

   1.0 EcoBoost 100/125/140 with cylinder deactivation (from ~2017)

   Ford added a 140 hp version and single-cylinder deactivation at low load, with a dual-mass flywheel and damped clutch disc to reduce vibrations. According to the Spanish press, this generation kept at least the oil-pump belt running in oil.^[1][11]

3. since 2019

   1.0 EcoBoost Hybrid 48V mild hybrid (125/155 hp, from 2019)

   It includes a 48-volt belt-integrated starter-generator (BISG) on the accessory belt that adds up to 50 Nm and allows the engine to switch off below 25 km/h (Stop-in-Gear); it earns the DGT ECO label in Spain.^[15][16][17]