1.0 ecoboost 125HP Negative LTFT at idle (-10%)

[cutin]

Hi all,

Could you double check that everything is okay with ECU because I have a negative long term fuel trims at idle around -10% and when I doing 3000RPM or more fuel trims are going to -3%.

Sometimes I see error P0420 (catalytic converter efficiency under range)

I reset ECU and during ride LTFT and STFT were 0% but when I stopped for long time on idle they went again to -10%.

Engine temperature 90*C,
MAF 1,7g/s i frequency MAF 2000Hz

Lambda sensor after CAT (screen)

 

[StealBlueSHO]

If the vehicle is stock, then you shouldn't be seeing -10% corrections. That means its pulling fuel to meet the desired AFR's. Couple that with your P0420 catalyst code, I suspect you maybe a leaky injector. This could be damaging your catalytic converter as the the raw gas will eat through the cats material.

Are there any other codes? Did any of the spark plugs have gas on them?

 

[cutin]

Yes, I could agree with this. I was my first thought - leaking injector.
Is any minimally invasive way how to make sure it's a leak? Disassembly to piece part level it will be the last chance.

I'm wondering about checking a fuel pressure in fuel rail after engine off because the any sensor on it.

I have a diagnostic tool Delphi DS150E and I can check some values until I will go deeper.

 

[TopherSho]

Pull the plugs,  not ideal but very informative,  it will be very obvious.  My suggestion is to wait overnight for the engine to be dead cold.. run it a few minutes idle,  rev it a tiny bit, then pull them .. bad plug will be wet/smell like gas and be very dark and or wet and or goopy