Dear all,
My car is Mazda 3 2016. The LTFT is always negative. I already change all spark plugs but it is still the same. What should i do to check where is the source of this problem? (i am going to change air filter as well).
I attached all information I can get from OBD port. Please take a look and give me some advices. Thank you so much
https://www.dropbox.com/s/0d2iupnelycbf2q/CSVLog_20210606_121719.csv?dl=0
https://www.dropbox.com/s/cu1aq0hxsyzevrt/CSVLog_20210702_171407.csv?dl=0
which engine please?
1.5L AT engine. Thank you
Negative means the engine is running rich
- Your MAF values are all over the place. Clean the sensor and see if they stabilize. If not, replace it with OEM
(also I don't know why you have two MAF columns. The second one doesn't make any sense)
- Your O2 sensor 1 (upstream) is dead. It shows nothing but zeros. Check the wires and connector. Replace with OEM if necessary.
- If those don't help then you could have a stuck fuel injector(s)
Thank you so much. I still have 2 more questions regarding to your responses.
- "Your MAF values are all over the place." --> What do you mean? I see that the MAF values are proportional to engine rmp. I already get it cleaned before getting the data.
- O2 voltage (Bank 1 Sensor 1) values are always 0. Upstream Oxygen sensor might dead as you found out. but I see that O2 sensor lambda wide range (current probe) (Bank 1 Sensor 1); O2 sensor current wide range (Bank 1 Sensor 1) (mA) and Heated Exhaust Gas Oxygen Sensor (bank 1 sensor 1) (µA) still have values so i got confused.
By the way, i will check everything you mentioned above as soon as i can. Thanks again.
You could be right about the O2 sensor. Maybe it only provides a lambda value instead of voltage.
MAF values
I am no expert, but to me it looks like your MAF reading is bouncing a lot when you are idling
here is what mine looks like
maybe this is normal for little 1.5L engine (mine is 5.3L). I'm not 100% sure. Maybe somebody else can compare
Thank you so much. I Appreciate. Hope someone else use 1.5L share the data