Nissan Almera N16 1.8 keeps stalling and throwing DTC P0171 (System too lean at bank 1)?Here's the history: No problems, then I got a K&N cold air intake system. I had to remove the MAF sensor from the old filter and put it into the K&N filter. All was fine until about a month later when the CEL came on. I plugged the car into my scanner and it came up with P0171. After checking this out i started to... |
Hi there, JP has given most of the info I would have supplied but using a live data scanner will help you too but forget voltage across the sensor check MAFS for volume, 1.0 - 4.0 g·m/sec: at idling
5.0 - 10 g·m/sec: at 2,500 rpm.
Also using the scanner you will be able to see the switching frequency of the front and rear O2 sensors, If the sensors switch fine, my thoughts from your description are MAFS related.
The amount of air the the genuine ECM is mapped for, deals with the amount of air passing through the original air filter body also reminding that air temp is involved too. By changing the air filter housing and air filter to a faster flowing K+N filter, the genuine ECM will fuel accordingly to the readings sent to it by the MAFS and will fuel as best it can but the Front O2 sensor see it as a weak mixture and lights the MIL, P0171 B1, what also happens now is that you will have also caused the cubic zarconia within the front O2 sensor to burn out and in the end you will have to fit your original airbox and filter new MAFS and front O2 sensor. OR fit replacement parts to your car now and refit your K+N and have the same problems in the future again if you keep the car.
Cheers
Andy
Not knowing what your long and short fuel tirms are doing. On Nissan we call A/F alfa readings of around 85 to 110% normal. If you have access to live data with that scanner watch air flow meter for over 4v peak at wide open throttle. Washing all that muck into the idle air control device is not a good move Use a rag and carburetor cleaner to clean the area where the throttle butterfly closes or remove the throttle chamber invert it and clean away with spray and brushes. I have had success cleaning the sensor inside the air flow meter on some cars but not on the Nissan AFM. I recommend K&N users to have two cone filters and allow the filter to completely drain the excess oil off before installing a dripping wet oily cone filter to ruin your next AFM.
