Oxygen sensors are they really necessary?
 

I am finding my car runs better with the Oxygen sensor removed?.
With it installed, the revs raise and lower and driving is awkward with stalling at slow speed manoeuvers.
With it removed the revs are more constant at 1,000 rpm.
Have checked old threads and this seems fairly common.
Is it just a case of replacing thimgs until you find the culprit? ( I have already deduced O2 sensors are all similar and so I can use a 3 wire Bosch for Ford or Buick, etc.

Or are fluctuating revs pointing to a particular area of concern?.

My "OLD" mechanic said he thought the DME was fried but then again he also wanted to charge me $3,500 for an oil leak repair! http://www.pelicanparts.com/ultimate/wink.gif
Thanks for any helpfull input Guys.
86 Carrera
rgds Ben

I too am running mine unplugged. Stable idle.

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Robert Stoll
83 SC
83 944

Unfortunately, the O2 sensor IS required on a Motronic engine, and the most likely culprit the Cylinder Head Temp sensor at cyl #3 ... see Pelican Tech Article.

Or, the following threads:
http://www.pelicanparts.com/ultimate/Forum3/HTML/004065.html
http://www.pelicanparts.com/ultimate/Forum3/HTML/004105.html
http://www.pelicanparts.com/ultimate/Forum3/HTML/004170.html



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Warren Hall
1973 911S Targa

Thanks Warren,
As I mentioned this seeems a common complaint that most like me ignor for more pressing tasks. But the list is getting whittled away and so the jobs at the bottom of the list are coming into view.
I will follow the threads and see what happens.
rgds
Ben

Yes, the Motronic is different from the CIS. Some CIS folks like to disconnect the sensor and this can work fine as long as the mixture is set properly.

With all Bosch fuel systems, there are step by step diagnostic procedures that are right on the money when something changes. I don't know which publications to recommend but it would certainly be my expectation that the Fabulous Bentley manual would have the factory Bosch steps and specs, unless they missed the target here as well.

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'83 SC

The Bentley manual is definately on my list for Santa this year!
Shall just have to make sure I put out enough cookies and milk! or maybe Swepco? http://www.pelicanparts.com/ultimate/wink.gif

Has you CO ever been properly set with a dwell meter?

Joe

Sorry, you've lost me there!

I shall try the Culinder Head temp sensor and if that does'nt seem to be the problem I will then look into 'setting the CO with a dwell meter'. Where will I find one of these or who would have one, is it an easy test?.
thanks for the ideas/help.
rgds Ben

Ragtop -- Ben,

One of the threads above has the testing procedure for the head temp sensor with a digital multimeter, so, if you get a valid resistance reading at the connector in the engine compartment ... you can look other places for the problem!

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Warren Hall
1973 911S Targa

Ragtop,

A bad oxygen sensor will cause the idle to fluctuate. I have run into that problem with other cars. You might try replacing it before you do anything else.

Steve

OOPS! I forgot we were dealing with DME and not CIS, so disregard my previous post.

Getting back to DME, my 86 3.2 will also surge at idle when I set the idle CO too rich.

Here's some more info on 02 sensors:
http://mr2.com/TEXT/O2_Sensor.html

Joe

[This message has been edited by stlrj (edited 12-10-2000).]