I'm having an odd problem with my 04 G35.
Both A/F sensors read near perfect a/f (approx 13.0) up to 5600 RPM, then the left bank A/F goes lean (off the chart lean like the injector turned off) and the right bank goes rich (approx 11:1).
THE ENGINE FEELS SMOOTH AS GLASS WHILE THIS IS HAPPENING. The engine runs strong.
No DTC error codes come up at all.
Any Idea's on what might be causing this?
Terry

 

Easy check would be for an exhaust leak.

 

the engine ia N/A (no forced induction) how would an exhaust leak matter?

 

If the leak is near the sensor it can affect the readings

 

OK, I'll check for a leak tomorrow.
Will I be able to detect a leak at low RPM?

 

If you have a leak, you will hear a hissing sound coming from the source of the leak at idle.

So I see you got you you've been waiting for right Terry?

.

 

I got it Henry, and if you want, PM me and we can run some log files on your car.

 

Bad sensor maybe.

 

Maybe a bad cat. I don't recall if you're running test pipes or not.

 

No test pipes, stock exhaust except for the addition of an extra sensor bung. (mabye that's where the leak is?)