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Auto o2 sensor .... replace or clean up?

Started by woodbowl, August 18, 2006, 10:27:01 PM

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woodbowl

I just had the codes pulled up for my 96 GMC Sierra pick up. I've had an occasional skip for some time so I changed the plugs. Wern't the plugs!

The code said it was an o2 sensor at the catalitic converter. I've heard that it may be possible to clean it up with a wire brush and blow it out.

Can anyone confirm this and tell how successful it may be?

I'm fresh out of $53's for o2 sensors this week.  :(
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Dale Hatfield

Don't know if you can clean it or not?
I figger if i have to crawl under take it out , clean it and put it back only to  do it again when the  cash comes in . It  also might takes a  special socket ,one that allows pigtail to stick out/ or not depends on the car
But I'm sure to tell you that you will save that money back at the pump. You will also find some lost ponies under the hood that ya forgot ya had.
Dale
Game Of Logging trainer,  College instructor of logging/Tree Care
Chainsaw Carver

woodbowl

I just came in from taking the o2 sensor off and putting it back on. It took about 20 minutes.

I've never seen one before, but it looks like a sheild with angled slots around the tip. Some of the slots looked clogged so I wire brushed it, tapped on it and observed a few particals comming out. Last, I blew it out with compressed air. I'll find out tomorrow if I did anything or not.
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

ScottAR

Replace,  they gradually lose their signal range till the computer
just starts ignoring them all together.  At which point, they are dead.

They work off ohms;  Say stoich is 3ohms, 1 ohm would be lean and 5ohms
would be pig rich...  Eventually, the sensor stops movin' back and forth and the computer just figures it's dead and quits lookin' at it. 

As long as the truck runs ok, I'd just run em till I could get em...

If the sensor is not a heated one, a box end wrench works fine. 
If heated, (bigger plug) either an open end wrench or they make a socket with a
gap in it.  Squirt on some RR or blaster or whatever as they sometimes are stuck.

Coat the new one with antisieze if it didn't come with any.
Scott
"There is much that I need to do, even more that I want to do, and even less that I can do."
[Magicman]

woodbowl

Quote from: ScottAR on August 18, 2006, 11:09:42 PM
Eventually, the sensor stops movin' back and forth and the computer just figures it's dead and quits lookin' at it. 

I've heard that if you disconnect the battery, the computor will reset itself.

Is there anything to that?
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

ScottAR

OBD I yes that would reset em... Pre '96
'96 up is OBD II  and it has to be reset with a scanner.
So you must buy, beg, borrow, or steal a scanner.  On the plus side,
OBD II is standardized, and will work on any '96 up vehicle. 
There's no rats nest of cabling needed unless you have an older car.


Scott
"There is much that I need to do, even more that I want to do, and even less that I can do."
[Magicman]

highpockets

Some years ago I had a Ford as a company car.  It had about 80,000 miles on it when it started acting like is was flooding.  I took it into the Ford dealer. They checked it and said it was an oxygen sensor but they'd have to order a replacement.  Since I was about 100 miles from home, I paid them $25.00 for their knowledge and left.   I drove that car until I left the company. At that time it had 185,000 miles on it and never another failure.  I contend that unhooking and reattaching the sensor cables was what fixed it.  I have always felt that the resistance was in the connections and unplugging them and replugging them made a better connection.  Low voltage is so sensitive to corrosion, ie resistance. I haven't done much auto work in years but I know most of these types of sensors used is what is called a wheatstone bridge to monitor gasses.  It is kind of like a filliment in a light bulb.  The resistance changes as the temp of buring gasses changes.  That is my story and I am sticking to it. 

Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

scsmith42

O2 sensors do go bad on occasion.  Woodbowl, you did the right thing by cleaning it.  Some spray carb cleaner will also help to get rid of the carbon.

On the older cars, disconnecting the battery cable for a few minutes will indeed erase the computer's memory.  So, try it and see how it does.

Good luck.  Scott
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

woodbowl

Today I found out that it had three o2 sensors around the catalitic converter, so I cleaned the other two as I did the one before.

One is located aft of the catalitic converter, one is located in the front and the third is located just before the pipe Y's together on the passenger side. Not sure how any of this makes sence.

Took it for a test drive and ............. no change.  :(  It still skips, especially when going slow up a hill.


Quote from: scsmith42 on August 19, 2006, 10:38:02 PM
Some spray carb cleaner will also help to get rid of the carbon.

Oops ....... I didn't think of spraying carb cleaner on them.

The sheilds didn't look burned out or rusted. Do you think if I soaked them in carb cleaner, they would start working again?

Or ...... is it possible that the computor remembers the history, causes it to continue to skip and must be reset before it can run right?

Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Modat22

I've had great luck by using Mopar catalitic cleaner on my O2 sensors. You have to buy it at the dealership and its not cheap but man its good stuff. My 95 truck had the O2 sensor fail twice and I ran a pint of that stuff through the system and it fixed it.
remember man that thy are dust.

ScottAR

'96 up generally have 3 or 4 if dual exhaust.  The rear ones are just
for emissions but will throw a code if dead. 

For carbon deposits, pull a vac. line and let the engine slurp up some
Seafoam or ATF and it'll clean all the buildup out.   Smoke like a forrest
fire while slurping and for a few minutes after. 
Scott
"There is much that I need to do, even more that I want to do, and even less that I can do."
[Magicman]

woodbowl

Been doing some searching and found a forum http://forums.bimmerforums.com/forum/showthread.php?t=324738  about o2 sensors. Most of these folks are cleaning the sensors with an electronic cleaner.
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Captain

If you are setting a O2 Sensor Lean code, it could be because of the misfire.

If you are setting a 02 Sensor Rich code, and the computer is leaning the mixture out, it could be causing the misfire.

O2 Sensors actually generate their own voltage potential based on the levels of Oxygen around the tip of the sensor.  Usually when a sensor fails, it is due to an outside contaminant such as carbon, silicone or glycol (yes, antifreeze).  Failures of this type almost always set the O2 Sensor Rich Code.

The shield you saw is designed to get a sufficient exhaust sample to the sensor,and to protect the fragile ceramic tip underneath.

Captain

woodbowl

Hey Craig, I'm glad you jumped in here. I took all 3 o2 sensors out today and soaked them for about 30 minutes in CRC electric cleaner, then tried to blast some pressure from the can into the slots for a final rinse.

One sensor is located after the cat, one located before the cat and the 3rd is upstream from the cat on the passenger side of the "Y" pipe.

If they can be cleaned up, is there a better way to do it? A better cleaner? Heat?

According to the code print out, it is one of the o2 sensors, but they don't know which one.  :-\ 
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Dangerous_Dan

Heat the tip with a propane torch to burn off the black deposits and crud. ;D
Don't use a oxy/acet torch, it's too hot and will wreck the sensor. :o

First you make it work, then you trick it out!

Captain

Olen, do you have a code number??  I'm pretty well connected you know....send me an IM.

Dan, that used to be one of my demonstrations in the training center.  I used a propane torch on an O2 sensor in the bench vise with a voltmeter hooked up to show the sensor working.  Sensor in the flame, rich (about 1V output) Remove the flame, lean (transition to 0V output).

Be careful with the heat as Dan said. A Cracked ceramic element is not a good thing for a closed loop system.

Captain

woodbowl

Quote from: Captain on August 22, 2006, 01:19:51 AM

Be careful with the heat as Dan said. A Cracked ceramic element is not a good thing for a closed loop system.


I thought about heating it with my propane torch to break the crud, but was unsure of how hot to heat it. I'm sure it could get cherry red after a while, but that seems like it should be too hot. ........   Is it?


Craig, the print out says:

History DTC  po140
o2 Sensor
CKT No Activity
(Bank 1 Sensor 2)
MIL REQUESTED
Since IGN   NOT RUN
Since Clear     FAIL
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Captain

In 1996 with the advent of OBDII there were four O2 sensors in your truck.

Your code referrs to the sensor just in front of the Cat. Converter as having insufficient activity.  This could be due to a contaminant, a wiring problem, or a failed O2 heater.

Captain


woodbowl

Hmmm ....  The auto parts wants to sell me that sensor real bad. In light of a wiring problem or failed o2 heater, is there a chance that it may not be the problem?
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

Captain

Easy enough.

At the O2 Sensor connector, he wires from the PCM should be Purple and Tan, for the heater pink and black.

With the connector disconnected....use a quality load, like a headlamp bulb, to test the heater wires for power and ground.  Should be present with the key on.
Then, ground the tan wire and measure for the presence of voltage on the purple wire with a DVOM.  With the tan wire grounded, it will be 350-500millivolts.  It will be much higher if the tan wire is NOT grounded.

If the wiring is good, the sensor is bad........

Captain

rebocardo

>  I have always felt that the resistance was in the connections and unplugging them

The 02 sensor breathes through the wire, if the connector is clogged with grease (put there on purpose) or from road salt and corrosion, then the wire can not breath. Unplugging it gets rid of the crud many times unless it has spread up into the wire.

woodbowl

Quote from: Captain on August 22, 2006, 11:26:40 PM
With the tan wire grounded, it will be 350-500millivolts.  It will be much higher if the tan wire is NOT grounded.


I haven't checked this yet, but the heater wires are OK.

Quote from: Captain on August 22, 2006, 08:19:50 PM
In 1996 with the advent of OBDII there were four O2 sensors in your truck.

Your code referrs to the sensor just in front of the Cat. Converter as having insufficient activity. This could be due to a contaminant, a wiring problem, or a failed O2 heater.

I replaced that sensor with a new used sensor.  ::)  ;D (cause I'm cheeep) and it still throws the same po140 code.

Now I've got an idea of how to make it throw a different code in the event I have one bad sensor. I had hoped it would zero in on the problem area.

There are 4 sensors. 2 are located on the left and right side on the pipe below the manafolds. The plug ins are flat style. The other two are located before and after the cat. These plug ins are square style.

I switched all 4 of the sensors location, according to the plug style, cleared the codes and the service eng light went off. Now I am expecting to recieve a different code # because the bad sensor must be at a different station point.

Not so ..... It throws the same po140 code.  smiley_headscratch
Full time custom sawing at the customers site since 1995.  WoodMizer LT40 Super Hyd.

gary

I fixed a car that did that to me also. It is very easy to fix .  You will need a pair of siissors, a tape measure and a roll of electric tape. Measure the  spot where the check engine light is. Then cut your electical tape to fit . place tape over the check engine light. You will never see it again. I drove that car for 5 years like that and never had another problem with the ckeck engine light comeing on after that fix.

sandrakerry

Your problem is probably a dirty mass air flow sensor. It is located in the intake air tube. Two very tiny wires measure the air flow into the engine. Clean with carb cleaner or brake cleaner. Do NOT NOT NOT use air pressure or anything else to touch them

PineNut

Gary, your repair also works for the low tire pressure light on my Toyota. I guess the light is still on but it hasn't bothered me for the past couple of years.

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