Hello. I own a suzuki swift 2011, 1.2 liter naturally aspirated vvt engine with 94 hp with 223000 KM on board (138 565 miles)
Recently I saw that my O2 main sensor is showing negative values like -0.045 mV. I'm guessing because of that, I also have -20% long term fuel trim and a rough idle. I've cleaned the MAF sensor with some MAF spray, I've cleaned the throttle body. Also I should mention that there are no codes at all, no check engine light no nothing, just me frequently checking some data.
If I rev it up, the long term fuel trim goes to about -9% but as soon as it is idling again, -20%.
This is all with the engine at operating temps.
The values of my MAF readings at idle are between 1.6 g/s to about 2.2 g/s. I saw that it differs depending on outside temperature.
How should I deal with this? Is the o2 sensor bad?
Thank you very much.
Well the show negative values when they are reading negative values more often it's a problem like leaking fuel injectors or some reasons getting too much fuel so then the computer subtracts fuel using the data it gets from the oxygen sensor
Thank you very much Scotty for answering. Can it also be a bad O2 sensor? I attach a screenshot with live data. Unfortunately I did not catch the o2 value but you have the injectors value. Also I will check the fuel injectors to see if they are leaking.
can you smell unburned gas in the exhaust?
Only at startup, but that's fairly normal. In the meanwhile, I have changed the fuel injectors and the O2 sensor, found some cheap from a wrecked car with 30k miles on it. My fuel injectors were visibly jacked up, the nozzle was looking weird. After this I went to a longer drive about 20-25 km. The long time fuel trim was about -5% but went to -10% when idling. The car feels a lot better to be honest. I have ordered a MAF sensor that will arrive in a few days. I will replace that also. My current one shows values of 1.6 g/s on idle which I think is pretty low. I cannot find anywhere some reference values of the MAF for this car.
The 2nd o2 sensor, after that CAT was showing values of 0.1v when cruising, and that's a good sign, very low hidrocarb passing the catalitic converter. The air/fuel mix at idle is oscillating between 14.4 and 14.8 which I'm guessing it's pretty good for a 10 years old 138k miles car. I will see what's happening after I change the MAF sensor.