How Would A TR Drive W/out O2 Sensors?

On a 91 USA Testarossa....how would the cars engine act if the O2 sensors were not plugged into the Cat Converters or test pipes?
Would it act differently when Hot Vs cold??
The reason why I'm asking is that I don't see them plugged into my Cats! And I have no air pump on the car...
Thanks

 

they were left out of my 512tr after a service once and the car was misfiring and shutting down banks etc. so i doubt it runs well without them.

 

Ah yes, a topic I have dealt with recently. I have a 91 Euro TR (which used to have a bad 02 sensor).

Sub 80c coolant temp, the system is open loop and the KE Jet ignores the signals from the O2 sensors.

Above 80c the system should go closed loop and begin to adjust mixture based upon the 0.1 to 1.0 volt signal coming through the o2 sensor wires (the 2 single spade connectors, not the AMP 2 pin connectors). You can test them if you want to see which o2 sensor is acting up.

There are a few write ups here on how to tell if your system is properly switching from open to closed loop.

If, like on mine, a bad 02 sensor was present, the car adjusted that bank's mixture based upon a faulty signal so it ran poorly. On my car, once I exceeded about 3500 rpm, the mixture signal got so out of line with norms the computer disregarded it and went to a basic non-adjusted setting. Conseqently, with a jolt, the car ran well from 3500 rpm up.

The rough running at low to mid RPM was driving my crazy and I could not find an o2 sensor locally. A friend who builds v12s for powerboat racing suggested I disconnect both sensors as one of them was giving a false signal. He reasoned that Ferrari would not design an engine which would grenade from a lean condition if an o2 sensor failed. He was right, the car ran far better that way on is base mixture setting.

I eventually changed both 02 sensors and the car ran even better. There are a few posts by me in the TR section when I tried to figure this out with the help of some of the more knowledgable people on the forum.

Good luck.

 

It really depends on how spot on your mixture is..

R

 

IIRC, it does not affect the Testarossas as much as the 512trs and 512Ms, mainly because the Testarossas does not use Motronic 2.7 system like the other two does.

 

It makes no difference if it is a TR or a TR512, if it needs the O2's to run well there is someting very wrong with the car. The O2's should only be making small temporary, short term corrections. If they are compensating so hard the car does not otherwise run well it should be fixed.


That is really true with any car.

 

My Euro 512 TR will not run with oxy sensors or thermocouple s disconnected........

 

Thats too bad.


I run 512s without O2s connected all the time.


Open circut on thermocouples makes the system think it is at max temp. Some models shut off Motronics if that happens but I do not recall if 512 is one of them.


I strongly suspct you are mistaken about the O2's. They are not required for the car to run..

 

Don`t think EPA would agree...lol - sorry brian, had to say it.

Car can run without O2 sensors connected as long as the base settings are correct (i.e. cam timing, idle air, mixture and balance.

If they are incorrect, the car will not run to well. but would also not run too well during cold start as any of the systems do not use the O2 sensor to adjust the mixture until the car is at operating temperature. the only variable is the richer mixture the ecu provides for the cold start.

As for the thermocouples, both plugs must be removed. if you leave the engine ecu to thermo ecu plug connected and only remove the temp probe plug it will read as max temp and shut down the bank. If you have cats, you should have the system working.

Regards, Jim

 

Then we are in agreement.

 

as always...

regards, Jim

 

just checked ! oxy sensors disconnected, runs rough. thermocouples disconected engine stops. This is a
Euro car without cats, test pipes have thermocouples fitted in......

 

Ah, I understand. My reading comprehension acting up again.

Yes I agree no reason to run without the. It is a matter of tuning and diagnosis when I run them unplugged.

 

If that is the case your O2's are working to correct a running problem. That is not their job and your car will perform better if you correct that situation.

 

Could I use my Innovate Motor sports LM-1 A/F meter to set my mixture? I assume I exchange the O/2 sensor with the wide band LM-1 one and switch back after tuning. Is this correct?





Ago

 

In my opinion an A/F meter is worthless in setting mixture. You need to see the effect on the other gasses. Using an A/F meter to tune is like cutting diamonds with blinders on.

 

Thanks for the feedback guys. Can you tell me where to buy the cheapest O2 Sensors for a USA 1991 Testarossa? Part number??

 

The "cheapest" would be a universal O2 sensor which wouldn't have the same connectors. IMO, you should buy the Bosch 0258003957 (which is the same thing as the Bosch USA 13009) -- it/they will have the correct connectors (except for they will be the same color; whereas, on the "official" F parts, one is white and one is black IIRC).

 

Thanks Steve! I'll try my local Napa or Checkers...thats all I have in Maui.

 

I found these online. Seems like a good price. I heard the part number was shortened to this new part number #13957. Does that sound right? Do the connectors look the same?
http://www.amazon.com/Bosch-13957-Wire-Oxygen-Sensor/dp/B000BZG7OM

 

Yes, I believe that Bosch USA 13009 and Bosch USA 13957 are equivalent (at least a search on those two part numbers brings up the same part at www.importeccatalog.com -- but that amazon price is better )

 

Would these work? Cheap at $18 each and free shipping!
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=360304310347&viewitem=&sspagename=ADME%3AB%3AWNASIF%3AUS%3A1123

I did find my O2 sensors on the bottom of my cats...duhhhh...so I do have them.

 

My experience with brand X O2 sensors has been universally disappointing. That is not to say we have not had difficulties with Bosch brand sensors but they have been better.

 

Bad move.. stick with the bosch sensors with the right plugs..

R

 

I used something similar on my 87TR about two years ago, not really any problems, But I don't think the heat shields will work with them. In the beginning I thought they were no good, but it turned out to be another problem, so it was nice I only spent the $30 or so instead of going for the full amount of the Bosch ones.