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Old 10-07-2001, 02:28 PM   #1
CUNNINGHAM
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Default Air fuel gauge prob?

I have a 98 25. I just installed a automete air/fuel gauge in my car and the gauge keeps going off the scale to the lean side and then up to the fist rich bar at idle. I have a super AF-C and I tried to richen things up too see if it will stabalize no luck. I used shielded cable from the ECU to the gauge. Could the gauge be screwed up or somthing else messed up.
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Old 10-07-2001, 03:29 PM   #2
Legacy GTR
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Default Nothing's wrong

There's nothing wrong with that. It's called cycling (among other things) It will do that basicly whenever your not accelerating hard. at WOT is when you want to see where the guage is at, then adjust your AFC accourdingly. What's happening is the ECU is leaning out the mixture to concerve fuel, then it needs to richen it, then it goes back to save fuel, and keeps going in that cycle.
One question for you now, does your guage lite up tons of lights at WOT at night or when it's cold? I have the same one and it does that, I think it's cuz the o2 sensor is not warm enough. But I tapped into the wire in the engine bay. Just looking for a confermation.
Mike
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Old 10-07-2001, 04:06 PM   #3
CUNNINGHAM
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Default Air fuel

Thank you for your help. I am a acura tec so I understand how the O2 works but I thought it the gauge would be a little more stable than it is for ease or reading, guess not.
I have read that on some of the cars it is recommended you tap into the second O2 which I have done and it help a little. I have been playing withe super AF-C and found I can stabilize it a little better with the addition of some fuel. It seems the car runs lean , for fuel economy reasons, and this causes the ecu to really search for optimum air to fuel ratio (the gauge jumping).
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Old 10-07-2001, 04:39 PM   #4
Legacy GTR
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your right, anouther thing subaru did is use the wide-band o2 sensors. I'm not too familer with the dirrference, but I know that the wide band is not as good for an A/F guage. One thing you might want to consider (if you have a turbo) is an EGT guage. If you don't have a turbo it won't be quite as useful.
Do you work for acura? Or just you used to mod integra's and stuff?
Mike
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Old 10-07-2001, 05:12 PM   #5
wac
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Default Re: Air fuel

Quote:
Thank you for your help. I am a acura tec so I understand how the O2 works but I thought it the gauge would be a little more stable than it is for ease or reading, guess not.
I have read that on some of the cars it is recommended you tap into the second O2 which I have done and it help a little. I have been playing withe super AF-C and found I can stabilize it a little better with the addition of some fuel. It seems the car runs lean , for fuel economy reasons, and this causes the ecu to really search for optimum air to fuel ratio (the gauge jumping).
The Subaru closed-loop program is very "stable". It just has a wide range that sometimes tends to exceed the sensitivity of some A/F gauges, but is almost always centered around stoich.

I would not recommend tapping off the rear O2 sensor if you have an MY98. The rear sensor always lags the front one, due to the catalytic converter being in the way. Like Mike said, just ignore the closed-loop stuff, and tune for open-loop only. The Subaru engineers knew what they were doing, since they managed to get almost 30 mpg hwy out of a 2.5L AWD car.

-WaC
Wayne
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Old 10-07-2001, 06:28 PM   #6
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Default

Yes I am a Acura tec at a Acura dealership. I am thinking of switching to a Subaru dealer fo obvious reasons.
So what you guy's are trying to say is get use to the wide swings of the Subaru O2 sensor and tune it for the open loop.
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Old 10-07-2001, 07:23 PM   #7
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Your on your way to being a Subaru Tech.
Mike
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Old 10-08-2001, 12:34 PM   #8
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If you watch the voltage on your SAFC of the O2 sensor you will see it fluctuate over a range..it corresponds directly to the mixture..higher # richer..lower # leaner.
I would not consider the Subaru Closed loop "stable"..its all over the place.
Like it was said, only tune it in open loop, above 25% throttle if I recall. Your AF gauge will give you a good solid reading and you can twaek it with your SAFC, thast what I do. My AF gauge BTW is the J&S dual monitor one.
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Old 10-08-2001, 09:19 PM   #9
CUNNINGHAM
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How do you hook up your S-AFC to the ECU to get O2 sensor voltages? I have heard of this being done but I never gave it much thought.
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Old 10-09-2001, 11:57 AM   #10
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you use the IN2 wire and tap into the frnt 02 sensor voltage..it is displayed in the etc. menu under sensor check
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Old 10-09-2001, 07:04 PM   #11
CUNNINGHAM
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IN2 wire, which color on the AFC is it . I lost the book.
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Old 10-12-2001, 12:33 PM   #12
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Default

Another question on the same subj.


I need help, 'cause I'm totaly confused to why my car is leaning out. It was fine for a logest time, and now it's doing it again.

Sometimes (not all the time) it would lean out around 3700 RPMS.
You can easaly feel it on like 3rd or 4the gear.

Another problem - after agressive driving my air/fuel sensor start BSing. You know how they usualy have red area, yellow area & green area. Well.... after I gun it few times it stays in low reds and wouldn't come up for a few minutes, but the car feels fine. later on (few minutes) the gauge acts fine again.

I already had the O2 sensor replaced under the recall that subaru had. but that didn't seem to change anything....

I don't have an SAFC installed. ASR had problems installing it for some reason.
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Old 10-12-2001, 11:39 PM   #13
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Stranger-IIRC an AFC won't fo much of anything on your car thanks to the voltage problem. I have not seen or heard of that before though. Try talking to Autometer(if that's where your guage is from) I heard they have good costomer support.
Mike
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Old 10-14-2001, 03:31 AM   #14
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Thanx Mike, I will try that.

A. aka Stranger
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