Hi

For many months, no one has been able to find the cause of the Focus engine problem.

1.0, gasoline, M1DD, 2015, 210e km

The attached picture shows live data from a 3-4 km city road.

The peaks are not important, it's just the gear shift.

The enrichment should always be around 14.7.

But when the engine is running without load, e.g. when stopped at a red light, the mixture is too rich, around 9.5-10.

The measurement was taken with a ThinkDiag device, which, when transferred to another 2021 car, gives textbook values, so I think the device is good for the car.

Fuel consumption is high, the exhaust is black, and the smoke is a little smelly.

It's not the lambda sensor, because when I put another sensor on it, it shows the same thing. (One sensor is Vemo, the other is Bosch, both are aftermarket).

It's not the catalytic converter because it was recently replaced.

It's not the spark plugs.

It's not the solenoid valve.

It's not the vacuum pump, because the original one wasn't working properly and was also replaced.

 

What could be the problem? Has anyone ever experienced this where the engine produce  too rich a mixture at idle speed? 

 But only at idle speed.

Thanks in advance

It's got to be a weeping injector then.

Try using FORScan 

On 12/8/2025 at 10:16 AM, DaveT70 said:

It's got to be a weeping injector then.

Try using FORScan 

thanks for yout reply,  injector is fine, it was cheched

Check air cleaner is not dirty, damp or blocked.

Clean MAF sensor

On 12/8/2025 at 6:13 AM, Roberthungarybudapest said:

It's not the spark plugs.

When were these last changed?

Throttle body? I recently had rich running but after cleaning carbon debris out of the throttle body my air/fuel mixture is back to close to normal? Ill probably replace mine at some point