2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

how bad will FCs run without o2 sensor?

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Old Aug 19, 2003 | 05:59 AM
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how bad will FCs run without o2 sensor?

somehow mine has burned itself off. don't ask how. was doing my downpipe last night and realized that the o2 was not connected to anything. (which explains why the sensor voltage in the safc never made sense, nor the o2 volt on the turbo timer either)

gonna go get one today hopefully, just wondering what the effects of this being like this were because it's been screwed for as long as i can remember. no wonder the guy before me had problems with the car.
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Old Aug 19, 2003 | 06:12 AM
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I would think it would make a pretty big difference, but I could be wrong.

My Haltech is currently running without one..
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Old Aug 19, 2003 | 06:46 AM
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It'll run fine, you'll just use ~5% more fuel.
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Old Aug 19, 2003 | 07:17 AM
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hey whould this help you run rich if you run a bit lean now? just as a temp fix until I can get an saf-c
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Old Aug 19, 2003 | 07:22 AM
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nz, are you saying that with the o2 gone, i'm running natually rich? or should i richen my safc a little until i replace that sensor?

just dont wanna run lean. my precat didnt have any soot in it at all, which kinda worried me. dunno how that could happen because my car would afterburn like hell on decel, must be leaning out somewhere in the throttle range though, right>
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Old Aug 19, 2003 | 07:29 AM
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The 02 sensor on FCs is basically only used when driving at a continuous speed, such as highway cruising. It is used to increase fuel economy. Basically the only negative effect you should have without one, is like NZ said, worse fuel economy. But no, you shouldnt run rich at idle or WOT.

*Edit*- And afterburn on decel could be a mal-adjusted TPS, or faulty ACV.
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Old Aug 19, 2003 | 07:36 AM
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Me car dosnt stay on with out a 02 sensor
i have a microtech mtx8
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Old Aug 19, 2003 | 07:39 AM
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Do you have an input from the O2 tied into the ECU for fuel regulation?

Last edited by Rxmfn7; Aug 19, 2003 at 07:49 AM.
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Old Aug 19, 2003 | 08:14 AM
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Originally posted by rx72c
Me car dosnt stay on with out a 02 sensor
i have a microtech mtx8
That's some seriously screwed up wiring...
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Old Aug 19, 2003 | 08:21 AM
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Originally posted by amused
nz, are you saying that with the o2 gone, i'm running natually rich?
Only a tiny bit more than if you had the O2 sensor working, and only in the light-load cruise situations when the ECU is normally in closed-loop and following the O2 sensor's readings.
or should i richen my safc a little until i replace that sensor?
No. Having no O2 sensor has no effect on idle, medium-load or high-load mixtures.
just dont wanna run lean.
The only time you need to be rich is under full load. The rest of the time you get the best results from relatively lean mixtures.
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Old Aug 19, 2003 | 08:31 AM
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So I guess my responses weren't good enough....

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Old Aug 19, 2003 | 09:20 AM
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****Me car dosnt stay on with out a 02 sensor
i have a microtech mtx******

Just another cheap aftermarket engine control system
Hey, all you guys make smart remarks about the factory engine managment system....so take that humor, please.

I had a irregular 02 sensor once. When cruising down the road I'd feel a ever so slight bogg when the 02 went off line(I have a led that shows codes inside the car so I can tell if it goes offline). With day to day driving you'll never notice it missing......until you go get the emission testing ...then you'll miss it big time.
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Old Aug 19, 2003 | 09:22 AM
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*****So I guess my responses weren't good enough.... *****

No, it was very good. The KIWI was just covering his *** on his first post. He meant no slight.
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Old Aug 19, 2003 | 09:53 AM
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i wouldnt' say it uses 5% more fuel ... i would say it uses 15% or more.

I went from 425 kms on a tank to 275 a tank when the 02 sensor wire decided that after my 2 nd time fixing it it would **** me off again.
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Old Aug 19, 2003 | 01:49 PM
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Originally posted by Rxmfn7
So I guess my responses weren't good enough....

he's just flowing the way a forum works

https://www.rx7club.com/forum/showth...hreadid=215695
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Old Aug 19, 2003 | 01:56 PM
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Originally posted by Cheers!
i wouldnt' say it uses 5% more fuel ... i would say it uses 15% or more.
I drove for 2-3 weeks without one and noticed no diff.

I guess my ecu doesn't use the 02 sensor much
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Old Aug 19, 2003 | 01:58 PM
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well it's definitely been not connected for a long time. i put my turbo timer in like a month after buying the car so what is that, may?

who knows. it pass a full inspection without the o2 though, go figure. that includes emissions
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