I have a 2008 Nissan Sentra with over 200k miles and while looking at the short term fuel trim and the fuel system status I notice the car idles low for a second and the stft drops from 24% to 0% and the fuel system goes from closed loop to OL Fault when this happens which is every few minutes to seconds, the cars idle changes and the motor sounds like if it’s burping all the way to the exhaust muffler pipe it does this at idle and while driving at any speed. What could be the problem with this? I checked for vacuum leaks but couldn’t find any but I will try different methods of finding leaks I really don’t want to remove the spark plugs it looks like a pain anyway please help me I’ve heard that it might be the fuel injectors or a cylinder misfire maybe cylinder 3 since I have a code for that but I erased it when I changed the catalytic converter and the code p0303 hasn’t came back since then it’s been about a month could it be the misfire I ignored thinking it was my cat????