Downstream o2 sensors
My o2 sensors bank1/2 sensors 2/4 show low voltage at idle. Doesnt really jump back and forth between .3 and .9 like the upstream sensors, itll sit very low at .05-0.15. is this a sign of old sensors that need replacing? They will jump in voltage if i rev, but its not a good pattern of back and forth switching, itll sometimes float at .8ish and slowly drop then go back down, sometimes switches for a bit, but overall not a good pattern.
No vacuum leak in engine bay, i going to check for exhaust leaks when i can. No engine codes. Idles smooth. This isnt normal though right? Mpg is maybe 20ish on very light driving, worse otherwise.
2004 g35 coupe 140.000ish miles
Fuel trims show +10-20 most the time on those sensors bank 1/2 at sen2/4.
Fuel trims show +/- 8ish on bank 1/2 sensors 1/3.
Either short or long trims, rear o2s show a positive amount stated above roughly.
K/n filter and motordyne 5/16 spacer.