Random O2 sensor question - PeachParts Mercedes-Benz Forum

meltedpanda · #1 12-09-2010, 10:20 AM

If you disconnect the O2 sensor when engine is at idle should you see any change if it is functioning as it should
THis is on another car I am working on , not an MB, but similar to the Kjet with lamda system.
And just what are the classic symptoms of a bad O2 sensor?

lee polowczuk · #2 12-09-2010, 10:24 AM

number 1 problem--- gas mileage dips signifigantly

number 2 problem--- engine can run a bit rougher at lower speeds

also you don't need the specific sensor.... you can get a generic one for less than half the price ... you just have to splice in wires.... no big deal

meltedpanda · #3 12-09-2010, 10:39 AM

thanks Lee, i was wondering about the generics, at ( in this case) a 3rd of the cost , I was skeptical
So as long as they are compatible, splicing in will work??
and disconnect at idle - you would or would not hear /see an idle disfunction?

This car has an idle issue and I have eliminated all other factors, so I am leaning to this sensor as a possible issue, my thought is that it is not functioning at all , it has over 75K on it
Getting it out may be the other issue -

samiam44 · #4 12-09-2010, 10:45 AM

If the sensor fails- the car should run rich. That's the default.

I would buy a universal replacement, but find the cheapest 2-3- or 4 wire sensor and cut and splice. I think in the 90's only bosch made them. For my old benz- a 1990 302 mustang sensor, cut, solder, splice and it works perfectly. It was about $35 versus a universal @ $55.
Amazon has great prices if you want to just replace it- about a 1/3 less than most of the online automotive places.

M

lee polowczuk · #5 12-09-2010, 10:47 AM

Quote:

Originally Posted by samiam44

If the sensor fails- the car should run rich. That's the default.

I would buy a universal replacement, but find the cheapest 2-3- or 4 wire sensor and cut and splice. I think in the 90's only bosch made them. For my old benz- a 1990 302 mustang sensor, cut, solder, splice and it works perfectly. It was about $35 versus a universal @ $55.
Amazon has great prices if you want to just replace it- about a 1/3 less than most of the online automotive places.

M

AGREED.

PB blaster works wonders if yours is stuck. My universal also had anti seize already on the threads.

KJZ78701 · #6 12-09-2010, 11:41 AM

Have any of you tested your O2 sensors using a propane torch?

Sensor in flame => no O2 => about 1 volt
move out of flame => O2 => voltage drops to about 0
Should drop within a few seconds if good

meltedpanda · #7 12-09-2010, 01:40 PM

flame test huh, sounds like a plan!

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