How serious can a bad O2 sensor problem become?
Dale Greep
O2 sensor will definitely cause this problem. Also, using silicone sealents
when replacing gaskets has been known to eat up O2 sensors.
<dan...@tstc.edu> wrote in message news:7b7d0f$6u4$1...@nnrp1.dejanews.com...
>I have a 94' Mazda 626 V6 (I believe it's the same engine in Ford Probe).
>About 5 or 6 weeks ago, the "check engine" light came on. Now it comes on
>within 4 minutes everytime I go past 2000 rpm or roughly 45 mph, and will
stay
>on until I turn off the engine. But if I am just idling or go slow, it
won't
>turn on.
>
>Anyway, I had a instructor of an auto class (I work for a tech.
>college)checked it out. They had a Code 15 and tracked it down to the
>front/left oxygen sensor. The manual says to use a multimeter to test the
>sensor. The first test says to rev the engine at 3300 rpm for 4 or 5
minutes,
>the voltmeter should read 0.55v. But we could not even get it up to 0.3v
(the
>pin connector was kinda greasy, they cleaned it a bit with a spray). So the
>instructor decided that the left O2 sensor was bad.
>
>Prior to the diagnosis, I had them replace my valve-cover gaskets, intake
>gaskets, spark plugs and wires. After they did the replacement, on two
>occassions I experienced strong, temporary vibrations of the whole car
while
>at above 60 mph. The first time my car shook so bad I thought I had a loose
>tire or bad balance and had to stop to check the tire. But nothing found.
And
>the car became normal as I resumed driving. The second time I tried to slow
>down to 40 or 50 and it was still shaking. I shifted into neutral and it
was
>still shaking. I kept on driving and after a while the shaking disappeared.
>
>The same day after the O2 sensor diagnosis, I felt the sluggishness taking
>off. when I try to go past 30 mph, it shook so bad and became so sluggish I
>had to stop several times. And 45 min. later, it was fine again.Daniel wang
>
>
>A friend told me that was probably caused by the lacking of oxygen due to
the
>bad sensor. Another said bad O2 sensor would only waste gas by making the
car
>run on richer fuel mixture. Rightnow, none of the autopart stores here
sells
>the O2 sensor for my model and Mazda's is so expensive. Will there be any
>consequences to keep on driving while I am searching for the part?
>
>Thank you very mcuh in advance!
>
>-----------== Posted via Deja News, The Discussion Network ==----------
>http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
dan...@tstc.edu
Robert Hancock
will cause bad gas mileage and may also cause fouling of the catalytic
converter, and it may need to be replaced as well.
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hanc...@nospamhome.com
Home Page: http://www.geocities.com/TimesSquare/Arcade/9967/
<dan...@tstc.edu> wrote in message news:7b7d0f$6u4$1...@nnrp1.dejanews.com...
sig...@ptd.net
. Will there be any
>consequences to keep on driving while I am searching for the part?
Dan,
My '93 Dodge Shadow had its O2 sensor go bad while driving to work. The car
lost power, shook like a tree in a hurricane...kept having to downshift to
keep it running til I got to work. Never got past 3rd gear (stick) the
whole time. I had it towed to the garage and was told I was "lucky because
it would've stalled and not re-started, had I driven another mile." It was
all I could do to keep it running, albeit quite slowly (no more than 20-25
mph). Cost me about $300 w/ parts and labor.
Chris Garcia
truck worked fine. I think this guy got hosed by a mechanic.
Chris
Mark Aarabi
> At most, you'll waste a bunch of gas. Mine was accidentally disconnected & the
> truck worked fine.
...And the survey says: "WRONG!!!!!"
"Wasting a bunch of gas" is certainly one of many consequences...but is not by any
means the "most" serious one. Prolonged driving with a faulty oxygen sensor can
cause a major "domino" effect. The excessively rich mixture can foul out your
spark plugs, cause carbon buildup, detonation, damage to the catalytic convertor,
and even EGR valve failure.
Keep in mind that a disconnected O2 sensor is VERY different than a faulty O2
sensor. A disconnected sensor would cause a reading of 0.45V (not lean / not
rich) and force open loop operation which would still render almost satisfactory
driving characteristics. A faulty sensor can cause the ECM to falsely "see"
either exremely rich or extremly lean conditions resulting in all sorts of
drivibility problems.
If you don't believe me, here's something you can try. Disconnect your O2 sensor
and ground the harness (ECM side) of the sensor and drive the truck for a couple
of weeks... (kids do NOT try this at home!). :)
-Mark Aarabi
ASE Master Tech
Robert Hancock
carbon monoxide poisoning :-)
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hanc...@nospamhome.com
Home Page: http://www.geocities.com/TimesSquare/Arcade/9967/
Mark Aarabi <maa...@bellsouth.net> wrote in message
news:36D76DA1...@bellsouth.net...
AJDalton7
>sensor. A disconnected sensor would cause a reading of 0.45V (not lean / not
>rich) and force open loop operation
How does a dis-connected sensor have a
reading of .45v?
Kevin Mouton
AJDalton7 wrote:
Because the O2S generates from 0.0 to about 1.0 volts depending on how much oxygen
is present in the exhaust. The more oxygen the lower the voltage. It does not need
a reference voltage applied to it to work.
Kev
--
To reply, replace "NOSPAM" in return address with "eatel"
http://www.eatel.net/~kevinm/homepage.htm
************************************************
Kevin Mouton - Automotive Technology Instructor
************************************************
"If women don't find you handsome they
should at least find you handy!"
Red Green of Possum Lodge
************************************************
AJDalton7
>> reading of .45v?
>
>Because the O2S generates from 0.0 to about 1.0 volts depending on how much
>oxygen
>is present in the exhaust. The more oxygen the lower the voltage. It does not
>need
>a reference voltage applied to it to work.
>Kev
>
Thats how it works. But how do you get
.45v ??
The sensor is reading o2 and that is dependent on how rich/lean the engine
runs.
The voltage of a diconnected sensor can
be of different values than .45v
Arthur
Mark Aarabi
> Thats how it works. But how do you get .45v ??
> The sensor is reading o2 and that is dependent on how rich/lean the engine
> runs.
> The voltage of a diconnected sensor can be of different values than .45v
> Arthur
This is true...A disconnected sensor will still have a full range of readings...
but that is unimportant here. What matters is what the ECM "sees" this reading to
be. In the case of a disconnected sensor the ECM "sees" a constant CENTER
condition (not-lean and not-rich)... This CENTER position is equal to 0.45V.
Hope this will clarify things.
-Mark
HANDZONTOM
SILICONE THAT WAS NOT O2 COMPATIBLE CONTINUED DRIVING IS NOT RECOMMENDED
dan...@tstc.edu
<sig...@ptd.net> wrote:
>
> . Will there be any
> >consequences to keep on driving while I am searching for the part?
>
> Dan,
> My '93 Dodge Shadow had its O2 sensor go bad while driving to work. The car
> lost power, shook like a tree in a hurricane...kept having to downshift to
> keep it running til I got to work. Never got past 3rd gear (stick) the
> whole time. I had it towed to the garage and was told I was "lucky because
> it would've stalled and not re-started, had I driven another mile." It was
> all I could do to keep it running, albeit quite slowly (no more than 20-25
> mph). Cost me about $300 w/ parts and labor.
>
Just replacing the O2 sensor cost you $300? That's expensive. But I think
Mazda dealers sell the sensor for more than $200, too.
I could only found a store (Hi/Lo) in town who could order it for me. It's a
univresal type Bosch, cost me $76. I found the instruction on a Mazda user web
site. Pretty simple for the left-sided one. I hope I will have the right tool
to do it myself. Some of the replies I got told me to solder the wires. I will
do so.
dan...@tstc.edu
<sig...@ptd.net> wrote:
>
> . Will there be any
> >consequences to keep on driving while I am searching for the part?
>
> Dan,
> My '93 Dodge Shadow had its O2 sensor go bad while driving to work. The car
> lost power, shook like a tree in a hurricane...kept having to downshift to
> keep it running til I got to work. Never got past 3rd gear (stick) the
> whole time. I had it towed to the garage and was told I was "lucky because
> it would've stalled and not re-started, had I driven another mile." It was
> all I could do to keep it running, albeit quite slowly (no more than 20-25
> mph). Cost me about $300 w/ parts and labor.
>
Just replacing the O2 sensor cost you $300? That's expensive. But I think
Mazda dealers sell the sensor for more than $200, too.
I could only found a store (Hi/Lo) in town who could order it for me. It's a
univresal type Bosch, cost me $76. I found the instruction on a Mazda user web
site. Pretty simple for the left-sided one. I hope I will have the right tool
to do it myself. Some of the replies I got told me to solder the wires. I will
do so.
daniel
Simon & Karen
about the fuel filter?
>>
>>
>Since my O2 Sensor was mostly reading lower than 0.2v at 3300rpm when the
>automotive class was diagnosing it, that means the engine was actually told to
>mix far more oxygen than it should have. And that was why I got the sporadic
>losing power or misfiring problem, right?
>
>Some people suggested my new spark plugs may not work well with the special
>mixture ratio, or my valve-cover gasket may have been replaced with O2-
>unfriendly sealant. So far as I know, the new plugs, plug wires, gaskets and
>sealants are OK. They were installed just two weeks ago. I used all genuine
>Mazda parts, i.e., plugs are NGK. And the instructor should know to use O2
>friendly sealant.
>
>Allow me to digress a bit, I got a more long-lasting problem since I bought
>this car a year ago. I have a sporadic shudder from the engine every once a
>while. You know how it feels when you turn on the AC on a old car and the car
>will sink a bit quickly? It fells just like that, though sometimes it could
>get slightly stronger. Sometimes it happends every 2 or 3 minutes, sometimes
>longer, or you don't even noticece it. People say this is misfireing, mayb be
>caused by many ressons, e.g., oil leak onto plug tip, bad plugs, wires,
>distibutor cap. But in the course of one year I 've replaced 2 set of
>plugs/wires, fixed the oil leak problem 2 weaks ago but could still feel this
>same engine glitch at any given time or any speed. There is no pattern of it
>so far. Note that this is a different proglem from my aforementioned "os2
>sensor related" shaking problem.
>
>I haven't checked the distributor yet. Do you gurus out there think it's
>related to this "glitch" / slight misfiring? Or could it also be related to
>the the O2 sensor (just recently had the "check engine" light on about 1.5
>months ago)?
>
>Thanks a bunch!
>
>Daniel
Simon & Karen
got 154K miles on it right now. Still passess California smog ok.
>>
>>
>Since my O2 Sensor was mostly reading lower than 0.2v at 3300rpm when the
>automotive class was diagnosing it, that means the engine was actually told to
>mix far more oxygen than it should have. And that was why I got the sporadic
>losing power or misfiring problem, right?
No its telling the engine there is not enough fuel going in.
>Some people suggested my new spark plugs may not work well with the special
>mixture ratio, or my valve-cover gasket may have been replaced with O2-
>unfriendly sealant. So far as I know, the new plugs, plug wires, gaskets and
>sealants are OK. They were installed just two weeks ago. I used all genuine
>Mazda parts, i.e., plugs are NGK. And the instructor should know to use O2
>friendly sealant.
Although anything is possible. I can't see why acetic acid, the solvent
in most silicon sealant, could hurt the o2 sensor.
>Allow me to digress a bit, I got a more long-lasting problem since I bought
>this car a year ago. I have a sporadic shudder from the engine every once a
>while. You know how it feels when you turn on the AC on a old car and the car
>will sink a bit quickly? It fells just like that, though sometimes it could
>get slightly stronger. Sometimes it happends every 2 or 3 minutes, sometimes
>longer, or you don't even noticece it. People say this is misfireing, mayb be
>caused by many ressons, e.g., oil leak onto plug tip, bad plugs, wires,
>distibutor cap. But in the course of one year I 've replaced 2 set of
>plugs/wires, fixed the oil leak problem 2 weaks ago but could still feel this
>same engine glitch at any given time or any speed. There is no pattern of it
>so far. Note that this is a different proglem from my aforementioned "os2
>sensor related" shaking problem.
inturuption of fuel delivery? check the filter
Robert Hancock
If it doesn't detect any change occurring in that voltage, it thinks, "we're
screwed" and sets a code.
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hanc...@nospamhome.com
Home Page: http://www.geocities.com/TimesSquare/Arcade/9967/
Mark Aarabi <maa...@bellsouth.net> wrote in message
news:36D8ABE2...@bellsouth.net...
dan...@tstc.edu
Kevin Mouton <kev...@NOSPAM.net> wrote:
>
>
> AJDalton7 wrote:
>
> > >Keep in mind that a disconnected O2 sensor is VERY different than a faulty
O2
> > >sensor. A disconnected sensor would cause a reading of 0.45V (not lean /
not
> > >rich) and force open loop operation
> >
> > reading of .45v?
>
> Because the O2S generates from 0.0 to about 1.0 volts depending on how much
oxygen
> is present in the exhaust. The more oxygen the lower the voltage. It does not
need
> a reference voltage applied to it to work.
> Kev
>
>
automotive class was diagnosing it, that means the engine was actually told to
mix far more oxygen than it should have. And that was why I got the sporadic
losing power or misfiring problem, right?
Some people suggested my new spark plugs may not work well with the special
mixture ratio, or my valve-cover gasket may have been replaced with O2-
unfriendly sealant. So far as I know, the new plugs, plug wires, gaskets and
sealants are OK. They were installed just two weeks ago. I used all genuine
Mazda parts, i.e., plugs are NGK. And the instructor should know to use O2
friendly sealant.
Allow me to digress a bit, I got a more long-lasting problem since I bought
this car a year ago. I have a sporadic shudder from the engine every once a
while. You know how it feels when you turn on the AC on a old car and the car
will sink a bit quickly? It fells just like that, though sometimes it could
get slightly stronger. Sometimes it happends every 2 or 3 minutes, sometimes
longer, or you don't even noticece it. People say this is misfireing, mayb be
caused by many ressons, e.g., oil leak onto plug tip, bad plugs, wires,
distibutor cap. But in the course of one year I 've replaced 2 set of
plugs/wires, fixed the oil leak problem 2 weaks ago but could still feel this
same engine glitch at any given time or any speed. There is no pattern of it
so far. Note that this is a different proglem from my aforementioned "os2
sensor related" shaking problem.
I haven't checked the distributor yet. Do you gurus out there think it's
Trapper
>In article <UiJB2.874$AP3....@nnrp1.ptd.net>,
> <sig...@ptd.net> wrote:
>>
>> . Will there be any
>> >consequences to keep on driving while I am searching for the part?
The )2 sensor is an enviromental device that protects your catalytic
convertor.
The following symptoms will help tip you off to a failed oxygen
sensor:
Surging and/or hesitation
Decline in fuel economy
Unacceptable exhaust emissions
Premature failure of the catalytic converter
>> My '93 Dodge Shadow had its O2 sensor go bad while driving to work. The car
>> lost power, shook like a tree in a hurricane...kept having to downshift to
>> keep it running til I got to work. Never got past 3rd gear (stick) the
>> whole time. I had it towed to the garage and was told I was "lucky because
>> it would've stalled and not re-started, had I driven another mile." It was
>> all I could do to keep it running, albeit quite slowly (no more than 20-25
>> mph). Cost me about $300 w/ parts and labor.
Find a new shop. O2 sensors are $80 a piece. I dont think your
problem is the O2 sensor, sounds more like the PCV or EGR to me.
Check your vacuumlines for starters.
Trapper
>>
dan...@tstc.edu
>
> >Allow me to digress a bit, I got a more long-lasting problem since I bought
> >this car a year ago. I have a sporadic shudder from the engine every once a
> >while. You know how it feels when you turn on the AC on a old car and the car
> >will sink a bit quickly? It fells just like that, though sometimes it could
> >get slightly stronger. Sometimes it happends every 2 or 3 minutes, sometimes
> >longer, or you don't even noticece it. People say this is misfireing, mayb be
> >caused by many ressons, e.g., oil leak onto plug tip, bad plugs, wires,
> >distibutor cap. But in the course of one year I 've replaced 2 set of
> >plugs/wires, fixed the oil leak problem 2 weaks ago but could still feel this
> >same engine glitch at any given time or any speed. There is no pattern of it
> >so far. Note that this is a different proglem from my aforementioned "os2
> >sensor related" shaking problem.
>
I gorgot to mention I installed a Mazda filter last year after I experienced
the problem. Didn't help. Since you mentioned fuel pressure, how do I check
it?
>
Thanks,
daniel
Simon & Karen
Wct 097
have to pull over then it would run fine, or run ok till I got up to 45 mph
then start shaking and shuddering. It turned out to be the mechanical fuel
pump. The spring had broken into 5 pieces and worked sometimes and didnt other
time. The shaking was due to detonation. If your fuel pump (probably
electric) was cutting out sometimes, it could cause the shaking, and could also
wear on your o2 sensor.
-Will
causa...@my-dejanews.com
Please help me, Sounds like you may have had the same problem I'm having with
my wife's car. 1994 Jeep Cherokee, 2WD, 4.0, Autotrans. Couple of problems:
1. While driving, it would act like it's running out of gas and when you let
your foot off the gas, it would run fine again. Some times, after the first
drive of the day, we would try to start it again and it wouldn't start.
Another time, it was wet out and kinda rainy, all the lights on the dash went
wacko and it wouldn't start until the next day. Currently it just sputters
and runs poorly, off and on. Two hours ago my wife called and said it stalled
out again. 2. None of our problems are consistant. 3. Had the engines
computer checked which reveiled an O2 Sensor problem. I replaced the O2
sensor about 2 months ago, yet the computer says it's bad. This past sunday I
had the Catalitic converter replaced (it raddled). The O2 problem didn't go
away with the new converter being installed. 4. I had the Injectors cleaned.
5. I had the Charging system checked. 6. I tested the O2 Sensor like the
shop manual said and it looks ok. I used an ohms meter on the two white wire
connectors. The needle went all the way over. I had an opportunity to test a
new one from the dealership which tested the same.
Does all this sound like something that would be related to the feul pump you
were
talking about?
Please help me in any way if you can. I would really appreciate it.
Thanks,
Craig
In article <19990302115824...@ng-ce1.aol.com>,
wct...@aol.comantispam (Wct 097) wrote: My Cherokee used to have a terrible
AJDalton7
Topmech11
lean when it's not you could damage the catalytic converter by flooding it with
raw fuel
jhe...@ix.netcom.com
failure of the engine - but please never spray anything on the O2 sensor.
Bosch has a good home page that describes how the sensor works but basically
you need to know a few things: O2 sensor has to be hot 300-600F to produce a
voltage. Some are heated and so they work right away but if they are not
heated then the engine control module runs on autopilot until its hot then it
looks for a signal from the O2 sensor to tell it how much fuel and air to mix
and if there is not enough voltage (varies) then it shuts down the signal
from the O2 sensor and turns on the CHECK ENGINE light.
If all of the O2 sensors fail then the ECM sets to LEAN and you'll notice a
rough idle after warm up. Make sense doesn't it?
Your engine needs all O2 sensors working and there is only one way to test the
sensor - heat it up (you can remove it to do this) and measure the voltage
(follow OEM specs). Insufficient voltage means its broken (not really but you
have to be Bosch to clean it). Replace it and have your old car back.
Now, be sure to not do the following: NEVER spray anything on the outside of
the sensor as the sensor must be clean and dry. NEVER spray silicone
anywhere it can get into the engine, carb, injectors, linkage, air filter,
etc. Silicon forms when combusted and it will coat the interior of the O2
sensor until it cannot take any readings. NEVER drive through water and
expect your O2 sensors to work - they may not work after being soaked. O2
sensors are very sensitive to trace metals like silicon, so keep anything
with trace metals away from the air intake.
Other causes of O@ sensor problems - some gasoline affect sensors - too much
alcohol, MTBE, oxygenates, etc as they can retain water and water has minerals
and minerals coat the O2 sensors. What to do? Just switch brands immediately
and see if the problem clears up. If not, replace the sensor.
By the way, I have not found any mechanics that test O2 sensors to see if they
are bad. So just replace it - it is easy and quick on most cars and the
unheated O2 sensors are cheap at less than $50 each and they make your engine
run perfectly.
J Hewitt
find what you need
@ www.hiperfuels.com
c_ch...@yahoo.com
the o2 sensor and the crankshaft pos. sensor. Then when I got in the car the
engine light turned on again. I turned the ignition to get the code and it
was the code for the O2 sensor again. I told him and he said he was sorry and
that he'd look at it today and get back to me. Well I get a phone call saying
that the "single board engine controller" (computer) is shot and they'll have
to replace it. I call the dealer and it's 535.00 bucks more. Just for the
part. Is this really going to be the problem this time? Come on ....Some one
out there, please give me some needed advise.....c_chaney@yahoo.com
In article <7bq96g$r4$1...@nnrp1.dejanews.com>,
Trapper
>On Sat, 06 Mar 1999 05:34:03 GMT, Mark Aarabi <maa...@bellsouth.net> wrote:
>
>>Seriously though... if you haven't found any mechanics that scope out an oxygen
>>sensor to make sure it is displaying the correct waveform and switching properly
>>before replacing it, then perhaps you should find a new mechanic. After all, how
>
>
> Mark, what is this about waveform? I just checked voltage on mine.
>Am I missing something here?
>
>
>Steve Best, Nova Scotia,
>4x4 van website:
>http://www.glinx.com/users/sbest
Not a thing he's overpromoting the expensive equipped shops that
charge you an arm and a leg for unnecessary tests.
This is what the real experts have to say about O2 sensor testing.
BOSCH
Technical Information Oxygen Sensor Diagnosis Generic Method
Here are some fast and reliable diagnostic procedures which you can
use to check out most oxygen sensors. A great time to do this is when
you are performing a tune-up.
The following symptoms will help tip you off to a failed oxygen
sensor:
Surging and/or hesitation
Decline in fuel economy
Unacceptable exhaust emissions
Premature failure of the catalytic converter
You will need the following equipment:
A handheld volt meter (digital VOM)
A propane enrichment device (propane torch)
An oxygen sensor socket
The manufacturer's vehicle specific test instructions.
It should take less than 10 minutes to perform a diagnostic check on
most vehicles.
1. Verify the basic engine parameters, per the manufacturer's
specifications for the following: timing, integrity of the electrical
system (supply voltage), fuel delivery mixture performance and
internal mechanical considerations.
2. Treat the rich mixture performance as follows:
a. Disconnect the sensor lead to the control unit.
b. Run the engine at 2500 rpm.
c. Artificially enrich the fuel mixture by directing propane into the
intake until the engine speed drops by 200 rpm. Or, if you're working
on a vehicle with electronic fuel injection, you can remove and plug
the vacuum line to the fuel pressure regulator.
d. If the voltmeter rapidly reads .9 volts, then the oxygen sensor is
correctly sensing a rich mixture. But, if the voltmeter responds
sluggishly, or if it stays below .8 volts, then the sensor should be
replaced.
3. Test the lean mixture performance as follows:
a. Induce a small vacuum leak.
b. If the voltmeter rapidly drops to .2 volts or below in less than a
second, then the oxygen sensor is correctly measuring the lean
mixture. But, if the voltmeter responds sluggishly, or if it stays
above .2 volts, then the sensor should be replaced.
4. Test dynamic performance as follows:
a. Reconnect the sensor lead.
b. Set the mixture to specification.
c. Run the engine at 1500 rpm.
d. The sensor output should fluctuate around .5 volts. If it doesn't,
replace the sensor.
Diagnosis When performing diagnostic work on your customer's vehicle
to determine the cause of a driveability problem or perhaps the reason
for failing an emissions test, take the opportunity to check the
operation of the oxygen sensor for proper functioning.
Recalling that an oxygen sensor will influence the air fuel mixture
preparation only when it has reached proper operating temperature (at
least 350oC), it is essential to first ensure that the engine and
sensor are warm enough to allow operation in a "closed loop"
condition. It may take as long as 2 1/2 minutes after cold start for
proper exhaust temperature to be reached (somewhat shorter for
heated-type oxygen sensors).
To check the performance of the oxygen sensor, run the vehicle engine
at about 2000 rpm (or at normal cruise when working with a
dynamometer) to ensure that the sensor remains hot throughout the test
procedure. Do not remove or disconnect the sensor lead in order to
test it as this will eliminate the "closed loop" signal to the
electronic control unit and result in a non-cycling voltage condition.
Using a correct electrical impedance test device as found with a
laboratory type oscilloscope, connect your test leads so as to read
voltage from the signal wire to the electronic control unit. With
vehicles that use a heated oxygen sensor (three or four wire), it may
be necessary to bridge the connector leads and tap into the signal
wire with an appropriate test probe at the connector plug in order to
obtain the signal. The oscilloscope will allow you to read the
electrical response pattern of the oxygen sensor to changing exhaust
gas oxygen content as a measure of its performance.
Before proceeding, be sure that you are using the correct measurement
scale for your specific equipment as specified by the test equipment
manufacturer. (Invariably, this will be a low voltage scale.)
A properly functioning oxygen sensor will exhibit a rapidly
fluctuating voltage signal alternating between approximately .2 and .8
volts in response to varying residual oxygen content in the exhaust
stream. Look to your scope's time reference line for a desired
lean-to-rich and rich-to-lean time of less than 300 milliseconds. A
response time greater than 300ms. means that the sensor should be
replaced. It is important to recall that these values are valid only
when checking a sensor operating in "closed loop" in a hot exhaust
stream (350o-8OOoC). Sensor age degree of contamination, mixture
setting, and exhaust temperature all have an effect on response time.
Without this rapid electrical response to changing exhaust
composition, the control unit cannot accurately correct the fuel
mixture. A sluggish sensor is either contaminated or beyond its
intended service life and must be replaced. Additionally, check
vehicle manufacturers' service recommendations and suggest replacement
of the oxygen sensor at specified intervals.
Oxygen Sensor Installation Tools In cases where installation position
is difficult to access, Bosch recommends using the following tools:
OTC 7189 Oxygen Sensor Wrench OR Snap-On 56150 Oxygen Sensor Wrench
(Crowfoot type).
Trapper
Mark Aarabi
> On Sat, 06 Mar 1999 05:34:03 GMT, Mark Aarabi <maa...@bellsouth.net> wrote:
>
> >Seriously though... if you haven't found any mechanics that scope out an oxygen
> >sensor to make sure it is displaying the correct waveform and switching properly
> >before replacing it, then perhaps you should find a new mechanic. After all, how
>
> Mark, what is this about waveform? I just checked voltage on mine.
> Am I missing something here?
>
> Steve Best, Nova Scotia,
> 4x4 van website:
> http://www.glinx.com/users/sbest
Hey Steve,
In most cases a good old DVOM will work just fine. In some instances, an oscilloscope
may be needed to give you the whole picture that a DVOM cannot supply. There is a
good drivibility article that I had read... just follow the link if you are interested
and make sure to look at the waveform links in the article:
-Mark
Mark Aarabi
> he's overpromoting the expensive equipped shops that charge you an arm and a leg for
> unnecessary tests.
That's a good one Trapper....
First of all... UNLIKE YOU, I am not promoting anything. Wasn't it just yesterday that
you were trying to sell some OTC noid lights (87 STANZA WON'T START thread) for
$54.95???? By the way, I bought the exact set from the MAC tool truck for $32...
Second, I do NOT charge an arm and a leg for doing diagnostics. As a matter of fact, I
have the lowest diagnostic fee in town.... and I am also the best equipped shop in
town. The reason I do this is that I love doing drivibility diagnostics, so I much
rather charge a little less and do a lot more.
Third, what is this about "unnecssary tests"? I admit that a DVOM is probably
sufficient for checking O2 sensors in MOST cases... but what about those hard to catch
drivibility problems (i.e. "it only does it when you go 37-38MPH under a light load
when its warm out")? You can survey ANYBODY here or anywhere else... and I guarantee
you that they would much rather do it my way (paying X amount of dollars for doing
proper diagnostic and then and only then replacing/repairing something that is really
the problem) instead of your way ("I guess it could be a bad O2 sensor... well it was
really the crank sensor... ooops the SMEC is shot") <=== SEE c-chaney's post on this
same thread.
Forth, wasn't it just a few weeks ago when you jumped all over somebody and called him
a ripoff artist for telling a poster on this newsgroup to change both head gaskets on a
3.8L Ford instead of just one??? I guess you also considered this an "unnecessary"
repair... Even though when you purchase a head gasket set it comes with ALL the parts
you need to do a complete job... and it takes so little extra time & effort to replace
both gaskets while you are at it than just one... and I sure as hell don't want to be
the one that would have to explain to a customer why he/she has to pay for the same job
TWICE in short span of time.
-Mark
Trapper
<maa...@bellsouth.net> wrote:
>Trapper wrote:
>
>> he's overpromoting the expensive equipped shops that charge you an arm and a leg for
>> unnecessary tests.
>
>That's a good one Trapper....
>
>First of all... UNLIKE YOU, I am not promoting anything. Wasn't it just yesterday that
>you were trying to sell some OTC noid lights (87 STANZA WON'T START thread) for
>$54.95???? By the way, I bought the exact set from the MAC tool truck for $32...
>
I wasn't promoting I was responding to someone who asked what a NOID
was. I simply clipped some text off an unknown website and sent it on
to him along with the pricing for his general information. No doubt
you can buy things cheaper but it's caveat emptor out there, it pays
to shop around.
>Second, I do NOT charge an arm and a leg for doing diagnostics. As a matter of fact, I
>have the lowest diagnostic fee in town.... and I am also the best equipped shop in
>town. The reason I do this is that I love doing drivibility diagnostics, so I much
>rather charge a little less and do a lot more.
>
You are different from some the outfits around here. I had a guy come
in a couple of weeks ago who had paid $80 for a O2 sensor test only to
be told it was OK when the ECU said it was not. It turned out to be
the atmospheric vent on the sensor was plugged.
Mark Aarabi
> I wasn't promoting I was responding to someone who asked what a NOID
> was. I simply clipped some text off an unknown website and sent it on
> to him along with the pricing for his general information. No doubt
> you can buy things cheaper but it's caveat emptor out there, it pays
> to shop around.
>
When I read that particular post I did not realize that you were just simply cutting &
pasting the info. from somebody else's web site. I am sorry for the misunderstanding.
-Mark
Trapper
wrote:
>Trapper wrote:
Must have been a bad day when I critcised you but unless one is
working with late model cars there is little need for expensive
diagnostics. Although I do agree there are times when you need them. I
don't work on many newer cars so I shop out the diagnostic work I
can't handle.
My belief is the best diagnostic tools a mechanic can have is his
eyes, ears and smell and lots of prior experience and a continual
ability to learn and retain that information. I was brought up on an
era when most of the shop equipment around today did not exist.
I can still align a car's steering without optical alignment equipment
simply because that how I was taught to do it. It's a little more time
consuming but just as accurate. Not that I promote it but it can be
done.
The more things change the more they stay the same as the saying goes.
The basics are still the same as they were on my first car a 1936
Wolseley Hornet. At least on that car you could set the timing and
mixture by levers on the steering wheel , so you learned about rich
and lean and advance and retard right from the start.
my apologies
Trapper