Should I bother to replug-in my oxygen sensor?

[Jimb]

My sensor has always been unplugged since I've owned the car and it runs beautifully. Now that I've pulled the engine and trans for a trans rebuild I'm wondering if I should bother to replace/plug it in?
It's an '85 carburetted.

Jim

[rlux4]

If it's carb'd it's been altered from original and if that's the case you don't have an ECU to receive the signal from the O2 sensor so it's not necessary.
Ron

[Jimb]

If it's carb'd it's been altered from original and if that's the case you don't have an ECU to receive the signal from the O2 sensor so it's not necessary.
Ron

No, it's original.
Carburator and supercharger.

Jim

[TX82FIAT]

Interesting that it had an O2 sensor? I thought that O2 sensor was only part of the fuel injection system. Maybe it was changed at the factory? In US I think all cars 80 on were FI.

[Europa]

This is interesting; click on the link below and look at the Production section. I didn't know 85's had a supercharger+carburetor option!

http://en.wikipedia.org/wiki/Fiat_124_Sport_Spider

[RRoller123]

Searched through Google images, but can't find a picture of this. Would be interested to see how they packaged it.

[rlux4]

Is this a Volumex? If so, being so rare it would probably be easier to get information about it on it from a site dedicated to the model. Most of them were sold in Germany, so it would probably be in Europe where such a site would be.
Ron

[Jimb]

Yes it is a volumex.

Well, when I reinstall the engine I plan to install a new sensor and plug it in. So we'll see what happens.
Cheers,
Jim

[narfire]

Hey Jim, I'll get the exhaust manifold boxed up here soon. Busy and cold at work. Perhaps send a note to Guy Croft as he re-builds the supercharger on the Volumex. Ital Motors in Edmonton....not sure if Mario would have an answer.
Thinking it through, I wonder where it would plug into. Is there the "computer" under the passenger dash in the Volumex? The supercharger pushes air through the carb , does the or can the carb make adjustments like the FI cars? I have a plug for the manifold.
Chris

[Europa]

Chris, it seems from the Wikipedia material it was an option to get the supercharger+carburetor. I'm wondering if the factory spec for an '85 was FI and the O2 sensor is just hanging there. I'd love to know if there's a ECU under the dash.

Jim, can you please post pictures of your engine bay?

[narfire]

I'm wondering if the factory spec for an '85 was FI and the O2 sensor is just hanging there. I'd love to know if there's a ECU under the dash.

I think you are right there. They took 500 total cars from 83 and 85, two colours only as well, and installed the supercharger. Might be parts left intact with the upgrade...

I've seen Jim's Volumex and it is indeed a beautiful example of fastidious up-keep. Not a squeak or rattle and nice smooth power.
Chris

[majicwrench]

I would certainly plug it in. Many many cars used carbs and O2 sensors, and the carb, with the aid of the ecm, then regulates the fuel mixture.
Methinks it would be hard to meet any sort of emmission spec with some mixture control.
It would be neat to know if the O2 sensor is simply left-over or if it is truly functional, but either way I would plug er in.
Keith

[Joe6pack]

I'll cast a vote for possibly not plugging it in. I have an '87 911 Carrera with an O2 sensor. When on the freeway at steady state, I always got a weird surging. It was really annoying. It turns out that it was the O2 sensor constantly adjusting the mixture. This lead me to do a lot of reading and experimenting. Generally speaking, an O2 sensor is only active under certain conditions. During warm-up or wide open throttle, they are usually ignored by the computer. At idle, cruise or part throttle is when the sensor reading becomes part of algorithm. When you unhook the O2 sensor, the computer substitutes a baseline (ideal) reading. As long as everything else is in spec, the car should run fine. I have a handheld air/fuel meter that I use to set any baseline settings. On a carrera, that is idle speed and mixture which are set with the O2 sensor unplugged anyway. For the record, European Carreras didn't have O2 sensors, so they clearly aren't entirely necessary. I was really nervous about unhooking mine as you are essentially taking away one of the car's senses. I have had it like this for about 3 years now and the improvement in driveability has been well worth it with no ill effects. As for O2 sensors on a Fiat, I can't speak directly to them except to say that they probably operate similarly.

Good luck.

[Jimb]

Thanks for the info guys.
Right now the engine is out but I will post of couple of pics of the set up as soon as I can for those who have asked.
Cheers,
Jim

[RRoller123]

I guess if it does no harm to run without it, and you don't have the pollution tests to pass, try it alternately connected and disconnected and see which mode performs better?