I have a 2011 Nissan Maxima SV with 177k miles.

It started to run rough yesterday. It actually alternates from 26 seconds of idling smooth to 4 seconds of idling rough.


Looking at the OBD II graph, the oxygen sensors all have odd readings:

O2S11: between 2.690v - 3.150v <- Way over the 1v expected max

O2S12: between 0.280v - 0.290v <- Very narrow range

O2S21: between 2.640v - 3.105v <- Way over the 1v expected max

O2S22: between 0.270v - 0.280v <- Very narrow range


Here's a graph from the OBD II scanner:




Does this indicate that all four oxygen sensors need to be replaced?

 

Also, the Short Term Fuel Trims for both banks are odd.

They switch from 25.0% when it is running well to 0.0% when it's running rough.

 

I would find it unlikely that all four would have failed. If you really suspect that any are faulty try changing one of the sensors that may be easier to change and check the results again. I would also expect a faulty sensor to throw a code.

 

The fact that they are actually changing values is usually (but not always) a sign the sensors are responding. I would check upstream for vacuum leaks, maf, and fuel system (injectors and pump). Could even be a bad plug or coil.

 

What's the status of your battery and charging system?

 

Great point. Jacked up voltages = jacked up results

 

Here is a bit more data to look at. This is the OBDII data for about 6 minutes from a cold start:


I had just changed the MAF sensor about a year ago with one from AutoZone @ $132.
The first two lines are prior to even starting the engine and the MAF is reading 1.18g/s which seems very high.
You can also see the OL_Fault every 30 seconds or so in the last two columns.

 

I had kept the original MAF sensor from last year when I changed it out. I put it back in and it's idling much better.

Here is a couple of minutes worth of warm data with a higher rev at the end.



It's still odd to me that:

• the Long Term Fuel Trim stays at 9.4%
• the Oxygen Sensor Voltages never get above 3.0v

It did solve all of the OL_Faults (every 30 seconds) and it is idling much smoother now.

I think the moral of the story is the aftermarket Mass Air Flow sensors are not good.

Thanks for the help.

 

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I am having nearly the EXACT issue on my 2009 Nissan Maxima, even after replacing one of the sensors, so I will look into the maf. Cant find a whole lot of info on O2 sensors reading 1.5-3.6v at all.