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  #1  
Old 12-08-2003, 12:07 PM
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Join Date: Aug 2001
Location: New Jersey USA
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Overriding an Oxygen Sensor

Greetings All -

Has anyone spliced the O2 wires togther to override the system? (White to white and ground the black)

This pertains to an 87 560SL. It seems that either the O2 wiring is bad or the cat. is plugged or faulty.

Has anyone experienced and/or solved my issue. It seems that when the car warms up the car looses all power and runs extremely ruff. All I have to do is pull off the Electrohydraulic Actuator connector and the engine regains all power per design (without the power of the EHA). Last time I had this problem I soldered together all the O2 wires and the problem went away. Unfortunately, water and oil got between the tape and I believe is causing a short due to the low/varibale voltage that is put out during warm idle and accelleration.

Thanks for any help!!

Russ
1987 560SL
165,000
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  #2  
Old 12-08-2003, 03:26 PM
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smoke gets in your eyes
 
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It's not the cat because pulling the EHA connector wouldn't fix a bad cat.

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum
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  #3  
Old 12-08-2003, 11:59 PM
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Hey Sixto,What are the symptoms of a plugged cat?
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  #4  
Old 12-09-2003, 12:16 AM
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Join Date: Apr 2001
Location: Joliet Illinois
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Not Recommended

I would not recommend connecting the wires together from the O2 sensor. Most sensors have three wires, one is the signal to the ECU and two are for the heater coil, used to help keep the sensor hot. If you send the 12v from the heater to the ECU it could be bad news.

The signal from a properly functioning O2 sensor to the ECU with warm engine should be a pulsing voltage approximatley 0.5v. The sensor generates this voltage on it's own, even without any wires connected.

Normally, just disconnecting the O2 sensor will put you in "open loop" operation and the car should run without electronic correction. Your fuel efficiency might suffer and the check engine light might come on but the car should still run.

John
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  #5  
Old 12-09-2003, 01:09 AM
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smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 19,759
Quote:
Originally posted by 420 benz
Hey Sixto,What are the symptoms of a plugged cat?
Basically the same as a restricted exhaust - fine off the line but difficult to rev under load. Sometimes accompanied by sulfuric/rotten egg smell.

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum
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  #6  
Old 12-09-2003, 09:02 AM
inspector1
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HO!HO!HO!HO!

OH! this is good! Are you for real santora4? This is gotta be a prank, nobody is dumb enough to short the O2.

We cant stop laughing here! Oh this too much!!!!
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  #7  
Old 12-09-2003, 09:13 AM
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Join Date: Aug 2001
Location: New Jersey USA
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Talking YIKES

My apologies!!! The way I wrote the thread does seem a tad crazy. I simply mean has anyone soldered together the wires instead of just unplugging the old sensor and plugging in a new sensor? Does the solder have any issues with such a low voltage?

Here are my symptoms:

1) The car will run beautifully for about 10 to 15 mintues.
2) Then the car becomes ruff then goes into a complete engine bogg.
3) I turn off the car then restart and the engine runns beautifully until I go through numbers 1 and 2 all over again.

It seems as if something electrical is grounding out or is it the classic symptom of a bad OVP relay?

Also, if I disconnect the O2 sensor (as stated in one of the threads) will the EHA be disabled?

I have been using the old trick; a 1990 Mustang 5.0 O2 sensor.

Does it take a lot of carbon to foul an O2 sensor or are they semi-durable?
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  #8  
Old 12-09-2003, 11:36 PM
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Join Date: Apr 2001
Location: Joliet Illinois
Posts: 309
Sorry, I misunderstood. Yes, I have used a mustang O2 sensor and spliced the connector on my Volvo because the Mustang sensor was about $90 cheaper. Most 3 wire sensors work the same, you just need to find one with the correct threads and tip length.

When splicing the wires, solder does not stick well to the signal wire (stainless steel or some strange material) so I crimped the connections and used heat-shrink tubing over the splice. That was years ago and it is still working fine. It's very possible for a soldered connection to go bad but it would be easy to just re-do the splice.

John
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