bryang37

Just curious if anyone else has a gauge (I haven an Ultra Gauge) that I monitor my vehicles with. I recently bought a 2012 G37 Coupe, 31,000 miles, very good condition. The gauges read very odd and I would like to compare. First of all, it will go closed loop very quickly, which is fine, but I have noticed that not matter if I've driven 5 minutes or 30, it will briefly show open loop when decelerating, at about any speed but most often about 50mph and start coasting (say downhill or to a stop). Has anyone else seen this? Also, my short term and long term fuel trims seem to be quite all over the map, but mostly about Srttr1 (-3.1) Srttr2 as high as (-8.6) (or higher) and Lngrt1 (-3.1) Lngtr2 (1.56). These very greatly so I have reset my gauge and will take better documentation. What I am also concerned about are the voltage rates as well, again they very greatly but today I documented them at mostly about:
02 V B1S1 broad 1.009
O2 V B2S1 broad 1.010
O2 V B1S2 0.720
O2 V B2S2 0.710


When the condition I mentioned (going downhill and coasting) I have seen :B1S1 2.000
B1S2 0.000
B2S1 2.000
B2S2 0.000


I have never seen this happen in my 2002 Expedition. It is always very steady. If anyone monitors theirs please post some average stats.


Lasty, one time (after 2 hours of highway driving, a 20 minute stop), then at restart I receveived a pending code P0159. Outside temp was about 50 degrees F. We finished our drive and 3 days later when we went to leave the same code popped up as I let my car idle to warm up before we left, it was about 25 degrees F at the time.


Any thoughts?


Never threw an actual CEL.

bryang37

Anyone have thoughts??

bryang37

OK, how about this then... does anyone use a gauge that can show open and closed loop? Do they notice it going open loop when coasting down a hill or decelerating?

Rr1982

iTrader: (1)

Decel is an open loop function. With about 100% Fuel cut,no need to read o2 sensors just the throttle position sensor 0% and Crank sensor for rpm . Unless you have a standalone which doesnt include open loop option, then the decel is programmed in by switching the function on or off based on vacuum parameters, read from a map sensor.

slartibartfast

iTrader: (7)

Fuel generally isn't cut off, just greatly reduced. Idle and closed throttle are usually a bit rich to compensate for poor turbulence in the cylinders which leads to poor mixing and rough running. No cat feedback is needed or wanted in these conditions, thus open-loop.

Rr1982

iTrader: (1)

Yes sometimes less fuel is added during deceleration to cool cylinder temps, but some do cut fully.

bryang37

Thanks for the insight! It is greatly appreciated.

SonicVQ

In the example of my G37 S (manual) when coasting with your foot is off the accelerator, it goes into open loop, commanded AFR is 0, measured AFR if 28-30:1, injector duty cycle is 4% with a pulse width of 0.72 ms.

So a tiny bit of fuel is still being injected.

As for when at idle, my car sits at a solid 14.6 - 14-8 AFR. The auto may be different due to increase torque requirement at idle.