how do you know your oxygen sensor is BAD???
 

is there a way to find out if the oxygen sensor is bad, without taking it in to a mechanic?

i've got a 1992 300CE with 166,000+ miles...
i'm not sure if the sensor has ever been changed (i'm third owner), but i am experiencing strange throttle response changes....in the morning after a good warm up, the car is peppy...but afternoon evening or after the car's been driven, the car is sluggish off the line...even hesitates sometimes...

i've notice a drop of 1-2 mpg also and all this happened so suddenly and quickly...within a 2 week period of time...

i read somewhere on ebay (a vendor selling non-spec o2 sensors by bosch (where you have to splice them in)) that gave all the similar symptoms i'm experiencing, and also pegged my mileage in the range when these things go dead... i.e., 10-12 years or 150-170k mileage....

is this true?
anyone?
please help.....

O2 element shoul read 450mV at 1500 rpm
heater should read 0,5-1,3 A
If not, replace

Cheers!

hey vronsky
in non-mechanic terms how do i gauge these readings?
i'm no mechanic nor do i have special diagnostic tools, but i am mechanically inclined and i am capable of doing minor/intermediate repairs without too mush of a problem...

so with that said how do i find out these readings again?

thanks

Find a multimeter that's sensitive enough to read millivolts, and ampere's. Pull out the cable that leads from the sensor at the small box (NOT at the downpipe), and read the voltage between the contact and mass/earth, while engine revs at 1500 rpm. Anything less than 450mV means replacing.
Next, pull out the cable of the heater element. Switch on ignition (do not start). Connect the brown cable to earth/mass, and the measure current between the other two contacts. That should read between 0,5 and 1,3A if okay.

Good luck.

Cheers!

hey vronsky
thanks

next dumb question...
is the o2 sensor located under the hood or under the car?

someone told me under the hood another said under the car
ugh
i've got a 1992 300CE

thanks

rich

Its either under the car or under the hood:D
If its under the hood, its mounted in the manifold with the cable leading to the area where the battery is placed.
If its under the car, the cable can be reached by pulling up the carpet under the left front seat.

Cheers!

mushedroom,

We're in this togethor, I am having similar problems and you asked this question before I could get to it.. nice work, btw did you ever find some thule racks for your car? Let me know !

There can be multiple lambda (Oxygen) sensors along the exhaust system. I recently attended a short Bosch training course on lambda sensors and posted this text when I got back:

For the record:
The lambda sensor's main purpose is to reduce emissions. It measures the amount of oxygen in a car's exhaust gases and adjusts the fuel/air mixture to compensate. If its voltage is low, the ECU sees this and richens the mix (longer injection duration) and vica versa if voltage is high, to get the perfect mix for clean combustion.

When working ok, and on constant throttle/idle, the sensor should alternate between high and low voltage around once a second (it is a simple device with no state for 'mix is just right').
Under acceleration, the ECU ignores it and adds more fuel, so in this case the sensor would be 'high' for too much fuel.
I won't go into more detail


in the post here:

http://www.peachparts.com/shopforum/tech-help/44233-california-officers-plug-into-your-car-see-how-illegal-you.html?highlight=sensor

good luck!

ok...
here's another question..
my car has always ran very very rich..i mean i can't stand behind the car for too long if it's warming up due to how heavy the exhaust fumes are...could this be a strong indication of an o2 sensor going awry?

i don't have any check engine lights on but these are my current symptoms...

1. random hestating/sluggish off the line performance
2. loss of 2-3 miles per gallon
3. heavy exhaust fumes (and i mean make you high and die heavy)
4. burning 1 1/2 quarts of oil 600 miles before next schedule oil change.

also an autozone sales person told me that if i change any exhaust items on the car, that would mean i need to change the O2 sensor too....is this true?
all i have done as far as modifying the car is change out my stock muffler to an arospeed muffler....

please help
thanks

oh also,

still haven't done anything on the rack for my mercedes....:(
the only one that i have found has been from mercedes and they want a million dollars for it... (ok just kidding but sheesh....700.00 is close enough...just for a bike/surf rack?????) :(

hey brandon, i'm still interested in a thule rack for my integra though....
please let me know
thanks

now back to this O2 discussion
thanks everyone

I will add that if an oxygen sensor is bad, I would expect a corresponding diagnostic code to be stored in the CIS controller. I think I got the following from JimF's website:

5 = Faulty oxygen sensor
17 = Oxygen sensor signal

These codes are easily obtained as explained in the D.I.Y. section and many posts on this website.

Mushedroom, I am no mechanic but I think your problems go far beyond an oxygen sensor. Seems like you may require major engine work...valve job or new rings.

hey bob,

how do you find these codes if you're not a tech or don't have access to a diagnostic machine?

thanks

I took the following straight from the D.I.Y. article by Steve Brotherton. You don't need a scope or an impulse counter. All you need is an LED wired between pin #3 of the diagnostic connector and ground. Mushedroom, if you need further help consider emailing me or even calling me.

______________________________________________

This process of reading codes for these early systems works up to 1994 for all systems, and later on some systems. Basically, it will work up to OBD II systems, and applies to all systems, not just engine management systems. The code retrieval method is very simple. The communications take place over a single line on the appropriate diagnostic connector. On the car I used (a 1991 300TE), the connector (X11/4) is located next to the battery, next to the right side hood hinge.

The KE controller is accessed on data terminal #3. With the key on, engine off, self-diagnostics is activated by grounding the #3 pin for two to four seconds. Once this takes place, the control unit transmits the codes by itself, grounding the #3 terminal. (Remember that all systems work the same; all you need is a directory of which pins to activate and the code table to interpret.)

The impulse counter makes life easy by counting up some high numbers. In the scope pattern in Figure 7, I connected the scope negative lead on the battery positive and the positive lead in the #3 pin.

I attached a jumper ground for three seconds and the control unit grounded the pin seven times, which could easily be counted. This was done again and code 13 was read, again and code 14 was read, and again and code 27 was read. If you are using the scope to read this, the time scale must be appropriate to get the whole thing, as every further activation moves on to the next code. They are listed one at a time until they are repeated. This can be done over and over. Each time the pin is grounded for two to four seconds, the next code is communicated by the control unit, grounding out the code number in "blinks." An LED can also be used to see a "blink" for counting. Once all codes are read, they can be erased by holding the jumper to the appropriate pin for six to eight seconds. After this is done, another activation with a two- to four-second ground will read the next code, and a further six- to eight-second ground pulse will erase it. This is continued until all codes have been read and erased. This will be shown by the final code of "one blink."

Mushedroom,
Email me with spec's...we'll figure it out

all,
I am experiencing the same symptoms and I know I will need a valve job soon because I have a tick at low oil pressure and sometimes for a few minutes after pressure is up. Does this mean That I am going to need a valve job before Sadie comes back to life? I have have been told by several mechanics that I can go a while with a ticking valve. True? wise?