Erratic Air Fuel Ratio Guage Behavior
#1
Drifting
Thread Starter
Erratic Air Fuel Ratio Guage Behavior
Dear All, (1985 US, 32V, Auto)
Well, I got my gauges installed and the AFR gauge (Autometer Phantom series) acts relatively erratic. I have a similar same gauge in 2 other cars and am very familar with how the gauge is "supposed" to read. In the my 928 however, the gauge seems like it is always "tracking" where it is suposed to go it just never settles down and is always bouncing around where it should be. I would think that if my AFR was really as jittery as the gauge is senseing that my car would run like poop so I think that I am picking up interferance somewhere. BUT I used shielded cable all the way down to the computer where I picked up the signal wire at and I tap the signal input for the gauge at the green whielded wire for the o2 by the computer and I also attached the shield of the input to the shield for the o2... In my head everything should be working fine, Can anybody think of anything that I am missing? Do I need to ground the shield again to the chasis by the computer? Thanks for the help.
Well, I got my gauges installed and the AFR gauge (Autometer Phantom series) acts relatively erratic. I have a similar same gauge in 2 other cars and am very familar with how the gauge is "supposed" to read. In the my 928 however, the gauge seems like it is always "tracking" where it is suposed to go it just never settles down and is always bouncing around where it should be. I would think that if my AFR was really as jittery as the gauge is senseing that my car would run like poop so I think that I am picking up interferance somewhere. BUT I used shielded cable all the way down to the computer where I picked up the signal wire at and I tap the signal input for the gauge at the green whielded wire for the o2 by the computer and I also attached the shield of the input to the shield for the o2... In my head everything should be working fine, Can anybody think of anything that I am missing? Do I need to ground the shield again to the chasis by the computer? Thanks for the help.
#3
Supercharged
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I'm not familar with that particular gage, but I had a Split Second AFR gage before and it does tend to hunt around a bit connected to the stock O2 sensor. I'd say it's normal for it to vary at idle from 14.3 to 15.5. My Innovate WBO2 sensor fluctuates from 14.5 to 15.0 at warm idle. Hope this helps.
#4
Rennlist Member
Per Autometer installation instructions, "When the Engine is at heavy load the moniter should indicate rich. At cruising load the minitor will appear to be bouncing back and forth between rich and lean. This is normal......."
#5
Rennlist Member
Also... "Since the oxygen sensor output is very accurate and sensitive at the STOICH A/F ratio, it will cause the A/F meter LED's to bounce back and forth rapidly." I thought that it should be steady myself when I first installed it.
#6
Three Wheelin'
Originally Posted by RngTrtl
Dear All, (1985 US, 32V, Auto)
Well, I got my gauges installed and the AFR gauge (Autometer Phantom series) acts relatively erratic. I have a similar same gauge in 2 other cars and am very familar with how the gauge is "supposed" to read. In the my 928 however, the gauge seems like it is always "tracking" where it is suposed to go it just never settles down and is always bouncing around where it should be. I would think that if my AFR was really as jittery as the gauge is senseing that my car would run like poop so I think that I am picking up interferance somewhere. BUT I used shielded cable all the way down to the computer where I picked up the signal wire at and I tap the signal input for the gauge at the green whielded wire for the o2 by the computer and I also attached the shield of the input to the shield for the o2... In my head everything should be working fine, Can anybody think of anything that I am missing? Do I need to ground the shield again to the chasis by the computer? Thanks for the help.
Well, I got my gauges installed and the AFR gauge (Autometer Phantom series) acts relatively erratic. I have a similar same gauge in 2 other cars and am very familar with how the gauge is "supposed" to read. In the my 928 however, the gauge seems like it is always "tracking" where it is suposed to go it just never settles down and is always bouncing around where it should be. I would think that if my AFR was really as jittery as the gauge is senseing that my car would run like poop so I think that I am picking up interferance somewhere. BUT I used shielded cable all the way down to the computer where I picked up the signal wire at and I tap the signal input for the gauge at the green whielded wire for the o2 by the computer and I also attached the shield of the input to the shield for the o2... In my head everything should be working fine, Can anybody think of anything that I am missing? Do I need to ground the shield again to the chasis by the computer? Thanks for the help.
#7
Rennlist Member
the guage is not doing anything. its the 02 sensor and the ECU closed loop that is creating this phenonenom. the ecu will measure the mixture and the ecu will tell the injectors to flow more fuel until the mixture is full rich, then the fuel is cut off where the mixture is full lean. this cycle happens 10 times a second! the average mixture ends up to be near stoich for best fuel economy and deposits reduction. when you go near full throttle, the system will go open loop where you will notice the ARM sensor showing full rich (near 12 to 13:1) you can also remove the O2 sensor, and have the mixture at full rich all the time (no hunting of the sensor lights), but your gas mileage will suffer
mk
mk
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#8
Formula One Spin Doctor
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Originally Posted by mark kibort
the guage is not doing anything. its the 02 sensor and the ECU closed loop that is creating this phenonenom. the ecu will measure the mixture and the ecu will tell the injectors to flow more fuel until the mixture is full rich, then the fuel is cut off where the mixture is full lean. this cycle happens 10 times a second! the average mixture ends up to be near stoich for best fuel economy and deposits reduction. when you go near full throttle, the system will go open loop where you will notice the ARM sensor showing full rich (near 12 to 13:1) you can also remove the O2 sensor, and have the mixture at full rich all the time (no hunting of the sensor lights), but your gas mileage will suffer
mk
mk
If the gauge is going back and forth indicating a change in mixture , this will be from the close loop operation of the factory ECU, if it bounces widly an irratically from very rich to very lean, this is a sign of uneven burn in the cylinders ( mis-fires ) from the uncontrolled combustion.......
#9
Drifting
Thread Starter
Well I guess it is settled then, it is acting normal....It is weird to me though on my truck and my (brother's and I) XR4ti the gauge does not bounce around at all it moves across the perimeter of the gauge with a definite purpose, very precise so to speak. In the 928 it moves in the appropriate fashion like in the other two vehicles, it just seeems too erratic to me. But having cunsulted the master this appears to be the norm in the 928. Thanks for the help ya'll.