Air fuel ratio of 4!

robzrr

Member
Joined
Sep 14, 2021
Location
Cumbria UK
TDI
POLO 1.2
My OBD Sensor reading (using a one from 'Torque') displays a value when the car is running and fully warmed up of around 3 to 4 :1 which is very low considering that the air fuel ratio of diesels should be around 14.7:1 to 15:1 . The 1.2tdi polo 6R is standard and has no smoke and runs ok apart from a little roughness between 1 and 2 thousand RPM and fuel consumption is around 50mpg which is a bit low for a bluemotion model. I suspect the Oxygen sensor is faulty...any ideas?
 

JELLOWSUBMARINE

Veteran Member
Joined
Mar 3, 2014
Location
yes
TDI
2011 Jetta Sportwagen, 6M, red/tan, navi, pano, 83 5m diesel pickup, 82 p/u trailer,.04 5.5 TDI Passat wagon (gone), 80,81,82 diesel p/u (gone), 80,82 sportruck (gone), 59 passthru bus (long gone), 79&87 westy (gone), 57 baja bug (long gone), 73 914
14.7 @ sea level is gasoline engine mix sweat spot.

Diesel still baffles me as it seems so much more adaptable/flexible. I'm not sure if diesel can be held to many of the same standards as gasoline. Its a ability to make more power by cramming more fuel into the mix is certainly different than gasolines ability.

FWIW I also noticed the same 4:1 ratio at different times with my POLAR F.I.S. My thinking is it must be normal operation or the soot load would be very high.
 

robertsean350

Member
Joined
Mar 5, 2024
Location
San Antonio
TDI
14 Passat
i have the same issue. a ratio of 3:1 would not result in combustion, yet the vehicle runs. we are missing a crucial piece of information. used the same tech on my rx8 no issues.
 
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