Disconnected oxygen sensor

SW??

Lester

 

These cars actually run smoother with it disconnected. It is 100% unnecessary on a 308 and dont let anyony tell you otherwise. Mine has been unplugged for 15 years. Same on my other three CIS cars.

 

Ditto to Dr. Tommy.

when the O2 sensor is plugged in you will get a slight occilating idle, the older the cat the more occilation... its runs much smoother with the non variable curve. also if you want a richer mixture you need to have it un plugged. ( not really that rich... )

more air + richer mix = more power... but we are only taking 1-2 Hp gain.if any.

 

If you install a new one everything and I mean EVERYTHING better be tip top perfect in that fuel system or you will have a subtle surge that will drive you out of your mind. You can spend a couple grand trying to smooth it out - maybe. Or you can unplug it for free. Really the only downside is you will go from 11 miles/gallon (normal) to 10.899 miles per gallon.

Don't fool with it. Leave it as is just hanging there.

 

You can adjust the mixture by hand without needing the O2 to do it for you all the time. My point is if you get a mix that is so rich it will burn the cat after it is unplugged it was way to rich before you unplugged it as well. Either way it needed adjustment.

If you live in an area that requires testing, plug it back in (takes only a moment), get tested, then unplug it again.

The surge thing is weird. You car will be trying to maintain a perfect air fuel ratio and since these cars are 30 years old, it is difficult to get all that to be dead on perfect even when it is in tune. When you drive steady it will feel like you are just slightly tapping the brake continuously. It can be very distracting and will just plain get on your nerves.

This CIS was an afterthought on this car for US emissions. The O2 sensor is another afterthought on this K-jetronic system again for emissions. In other words this motor etc was NEVER designed with it in mind from the beginning like fuel and ignition systems were just a few years later along with the on board computers to run everything properly.

On 198-anything 308 you can just disconnect it, fiddle with a thing or two on the CO and never worry about it again since it really wasn't supposed to be there to begin with. The same thing cannot be said on later, more modern cars.

 

Or you could set the base mixture as specified, ensure that the lambda control box and FV are working correctly, replace those drippy injectors with ones that spray correctly and enjoy dramatically better fuel economy, performance and not be a gross polluter for no good reason. And yes, these cars can have a mild steady state perceived lean surge if the base mixture is too far from stoichiometric. With a duty-cycle meter and a exhaust gas analyzer, the car will run extraordinarily well. The Bosch K-jet with lambda works exceptionally well and is dead nuts reliable. Ten of millions of cars from the 80's use this system with virtually no ill effect. And it's not normal for any 308 QV to 11 mpg under normal conditions...

And the O2 sensor does not set the mixture. It measures the oxygen content in the exhaust, creating a voltage which "tells" the lambda box to adjust the mixture, based on an internal reference. Modern cars use this method of feedback because it works exceptionally well. Today's sensor and computers work considerably faster than the ones that were used in the 80's though...

 

another solution is to buy 4 webers

 

Works for me!

 

My appendix doesn't do anything either. I think I'll just cut it out and tape it off.

My car is in Dave Helm's shop right now. I have a surge with the O2 sensor plugged in, but that didn't prompt me to unplug it. Rather, I took it to Dave to sort out the CIS. He's gathered numbers from the exhaust sniffer tubes for each cylinder and they are all over the place.

Fix the problem at the root cause before you tape off your appendix.

 

Well, I think this thread is what they call a storm in a tea cup. I've had mine tested with it un plugged and plugged and its passed GA emissions... so I really dont see the issues here.

In my 308, the surge was so noticable even after a full rebuild - engine, CIS etc... un plugged for me was the way to go.

 

I suppose I was only slightly off but I didn't pull 11mpg out of my ass
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Everyone should do all that anyway.

 

On a vehicle of this age the injectors can get gummy or a bit of grit in there and have a less than ideal spray pattern, I think also if the spring inside goes soft it can drip down after shut down. This can be especially true for our cars that sit a lot. They may be fine but at this age, age may have taken its toll on the injectors doing their job properly.

On replacement and where to get them, I'll leave that to your reading pleasure. I've read past threads on that and don't feel qualified to summarize.

 

As Dave said I also found to be very true. New Lamda sensor, proper tune and it runs like a dream.

 

Image Unavailable, Please Login Chris, not sure mileage on your 308 but my nearly 50k mile 328 had a lot of dingy gummed up injectors. Working on replacement right now, bushings, orings and injectors(new) ready to go into newly painted manifolds as we speak along with replaced vac hoses among other while you're in there things. Bought 10 injectors(same as yours) and had them tested and picked the best 8. Bought bushings from a source here, no longer available, but the guy Robzworkz used seems to have a great product. My bushings were a mess, injectors loose due to that and bushings, and other vac hoses very old so going as well. Again, happy to assist any time, I'm no mechanic but had mine 6 yrs, pm me if want some assistance. I use Emilio locally now, Italian mechanic but mostly not Ferrari, but I feel capable to fix much of what ail our cars......one of my dirtier injectors.....

 

I'm sure that might have hurt...Then again, next you're going to tell me that a) you actually believe the EPA numbers b) you believe the Ferrari stated HP numbers and c) the weight listed in the OM is correct. Regardless, unless your 308 is sporting a 12-cylinder carb engine, I'm having a tough time believing that the number is a meaningful average. I would expect to set about 15-17 on average with a properly set-up engine.

 

My 328 averaged 22-23 MPG on a 2700 mile cross country trip. Speeds on average were noticeably above the posted interstate limits (and in sections of NV/AZ they were waaaay above the posted limit). I have never checked it in town. Can't think that an injected 308 would be much different.

 

Why am I going to tell you those factory numbers are correct? The BASIC question on this thread was is it ok to disconnect an O2 sensor on a 308.

The answer is yes. It is perfectly fine to leave the wire hanging. Even after extensive dx and tx of the system, doing so often makes the car run better.

If you want school me on hp and weight, start another thread ( and when you do ill tell you a 2V inj is about 20-25 hp less than what Ferrari wanted us to think)