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Thread: O2 Sensors
12-08-2010 01:20 AM #1
2002 330i 63k miles
Time to fix the O2 sensor issue fellows, and I need your help!!! If you recall, I had to replace the valve cover gasket a while back because of leaking, maybe 6 months ago. One of the "sharpies" on this MB noted that I should have not used the red gasket sealer. He wrote there is a special gasket sealer for cars with O2 sensors. He was right.
When I went to start the car after the valve cover job, the car ran very rough for about half a minute. Coincidentally the original battery failed just while sitting in the garage for the couple days I did the valve cover job. I thought replacing the battery caused everything to "re-adapt" hence the rough running for about half a minute. Maybe not... maybe it was the gasket sealer (Permatex High Temp Red RTV Silicone gasket maker) that screwed up the O2 sensor/sensors???
The "check engine soon" light came on right after doing the valve cover job. It had never come on before. At first it was intermittent with no particular pattern, always different, a couple days it did not light at all. But it pretty much came on every day for most of the driving time.
I ran my code reader back then and only these 2 codes came up in this order: E4=Adaptation Limit cyl. 4-6, E-3=O2 Adaptation Limit cyl.1-3. Only those 2 codes for a couple months.
NOW... the light is staying on full time, and the engine seems slightly rough at idle. Time to fix this problem. So tonight I ran the codes and got the same E-4 and E3, -but also got a C-6 code-= Cat Efficiency cyl. 1-3. And all 6 codes for all 6 cylinders misfiring.
So gentlemen... where do I start? Which O2 Sensors should I replace? As always, thank you very much!
12-08-2010 02:37 AM #2
First of all your car is young at heart, at least
in miles if you have not beaten it while driving. Most of your equipment has not reached the end of their life cycle, and I would guess your 02 sensors are included in that. (with an expected life of at least 100,000 miles)
Next I'll hazard the guess that the sealant you used is not responsible for the rough running.
Now I'll say that your maladies are complex enough to warrant a service trip to your local knowledgeable BMW dealer with a mechanic who works on these complex engines all the time and has a better feel for what goes wrong and what it looks like than we ever will from the long distance we are from your engine. This is not the time to become the quick change guy on your block! It might become way too expensive even without finding out what is wrong.
Please come back and let us know the ultimate solution you find is correct?
Footnote: a new battery does not affect the initial start-up of your engine.
12-08-2010 12:58 PM #3
I'm a gambler at heart!!
For an engine that is 10 years old with 63,000 miles, I'm going ahead with replacing all 4 oxygen sensors. It's a easy job, you just unbolt them and plug in the connectors. I bought them from Autohaus who had excellent prices on the genuine OEM Bosch, $66 each fronts, $68 each rears (more correctly pre and post cats). The text below (very informative) from Autohaus website states about the silicone gasket sealer. -- Either way, whether they work or not to solve my issues, they will have all been replaced and hopefully that issue will not come up for another ten years.-- We'll see... right boys? Besides, we are CAN DO on this MB, now aren't we???? (:
Oxygen Sensors Don't Last Forever
Here's What Happens As They Age
As an oxygen sensor ages, contaminants from normal combustion and oil ash accumulate on the sensing element. This reduces the sensor's ability to respond quickly to changes in the air/fuel mixture. The sensor slows down and becomes "sluggish".
At the same time, the sensor's output voltage may not be as high as it once was, giving the false impression that the air/fuel mixture is leaner than it actually is. The result can be a richer-than-normal air/fuel mixture under various operating conditions that causes fuel consumption and emissions to rise.
The problem may not be noticed right away because the change in performance occurs gradually. But, over time, the situation will get worse, ultimately requiring the sensor to be replaced to restore peak engine performance.
Oxygen Sensor Failures Can Mean
Big $$ In Repairs If Not Replaced
The normal aging process will eventually cause the oxygen sensor to fail. However, the sensor may also fail prematurely if it becomes contaminated with lead from leaded gasoline, phosphorus from excessive oil consumption or silicone from internal coolant leaks or using silicone sprays or gasket sealers on the engine. Environmental factors such as road splash, salt, oil and dirt can also cause a sensor to fail, as can mechanical stress or mishandling.
A dead sensor will prevent the onboard computer from making the necessary air/fuel corrections, causing the air/fuel mixture to run rich in the "open loop" mode of operation, resulting in much higher fuel consumption and emissions.
An additional consequence of any oxygen sensor failure may be damage to the catalytic converter. A rich operating condition causes the converter to run hotter than normal. If the converter gets hot enough, the catalyst substrate inside may actually melt forming a partial or complete blockage. The result can be a drastic drop in highway performance or stalling because of a buildup of backpressure in the exhaust system.
12-08-2010 02:45 PM #4
DONT CHANGE YOUR SENSORS YET!!!
Before you spend $250 and a Saturday afternoon on cold concrete, check the condition of the duct between the airbox and the intake manifold. This is two lengths of flexible rubber hose about 4" in diameter connected in the middle at a swivel point with hose clamps. Use a flashlight, mirror, and your fingers to see if you have any cracks, holes, etc. in the ducting (even little ones will eventually trip service engine codes). The bottoms of these in particular (where they are hardest to see, reach, and feel) rot out letting unmetered air into the system. This unmetered air will trip E3 and E4 codes. both sections of the duct will only cost about $60. The section closest to the airbox is a 15 minute replacement. The lower section is a bit tougher (but not too bad). I have a 2001 330i with about 71K miles. So far, I've had to replace the duct piece closest to the airbox twice. If you are tripping these codes almost daily, I suspect you will find significant holes in this ducting.
12-08-2010 08:53 PM #5
Dead Ed, is most certainly NOT BRAIN DEAD!!!
Ok I thought... the sensors are still $250. That's still some good coin. So I read DeadEd's post, and immediately called Autohaus and told them to hold my box for one day. They said they could not, only to cancel it, so I cancelled at no expense to me.
I had to wait until my wife came home tonight with the car. I thought no big deal taking out the air box, ten minutes, I'll clean her K&N filter right away. So I got the filter box out, and what do I see??? No, no cracked hoses, just the big cold air intake totally off and away about an inch from the alternator cooling duct. Jackassses at the Stealster. We had the alternator replaced under the CPO warranty a couple years ago. The so called BMW tech just simply never put it back on. Could of it fallen off? Absolutely not, the duct fits together very tight, and I had to wrestle with it for about a minute. No accident, he just didn't bother to hook it back up! Amazing. The Stealster. But we were happy for the alt. All it had was a bad bearing that would only make a grinding/scraping noise when -cold only- for -only a few minutes-. Sounded exactly like a water pump bearing. So instead of just pressing on a new bearing, we got a whole new re-built alt. But I digress...
So I fixed that, and went on a hose hunt. Nothing down there. I knew I had to follow the main big bellows in behind the mass air sensor. That big bellows looked good and pliable. Two small lines come out the top of this bellows, all looked fine. These both go from rubber tubing to metal in a short distance.
But waaay back in, almost against the firewall, a -second much smaller bellows hose arches in to the left toward the engine. Looked it all over, seemed flexible too. Just about ready to call it a day and put it all back together when I remember DEAD ED saying to feel all over, and even use a mirror.
I thought what the heck, I have a little dental mirror that my dentist never missed. (; Holding it behind this small bellows hose on the outside curve where all the strain would be... bingo! Several small cracks, three near one groove, and another crack up one groove. And that's only what I can see with the mirror at this point.
So... HATS OFF TO DEAD ED. THANK YOU VERY MUCH ED!!! YOU DA MAN!!!
I'll put it all back together for now until the parts arrive. Then I'll let you know the results.
12-08-2010 09:48 PM #6
Excellent that you found the problem, hopefully.
You might have put some duct tape over the cracks on the inside of the bellows temporarily to see if that changes things.
You've hit upon another of my pet peeves. Mechanics who don't pay attention are all too common. Sleep walk thru the job that you're paying them $100/hr for. I've had it happen too many times that I have to go back over their work to make sure my car is together properly.
That's why I hate to let my car disappear into the dealer's bays without me.
12-08-2010 09:50 PM #7
12-08-2010 08:07 PM #8
Autohaus has great pricing and I'll be buying 02
sensors there myself when I need them. But also remember they are in business to SELL sensors, so take with a grain of salt the dire picture they paint of a failing sensor.
I've got an almost 7 year old car with 77K miles and I just hooked my car up to a friend's PC with diagnostic features that allow you to read the real time output of the sensors. All four sensor outputs were right in the center of the correct operating range! I'm still betting your sensors are not the problem and urge you to try the inspection that DeadEd suggested right below here.
Just to establish common ground, the pre-cat sensors are really the only ones that count with regard engine management. They are the primary feedback sensors. The post-cat sensors are there mostly to monitor whether you are exhausting clean air for emissions purposes. You could care less about these as far as proper engine running is concerned.
All that said, I like to replace parts ahead of time to keep all pure myself, so by all means put your new sensors in. What I'd really appreciate is if you come back here and describe if that changes things, or whether you have to continue to troubleshoot your car to find what ails it.
12-08-2010 07:40 AM #9
O2 Sensors ? not
the O2 sensors are just mirrors of the motors
performance - or lack there of (chicken or egg ?)
the trouble starts up stream,
something with the motor mechanically, controling electronics,
fuel delivery electronics ........
this is the reason your code reader is ineffective
you need the power of BMW shop diagnostics
to zoom right in to the exact cause for the
down stream O2 sensor messages
get it to a dealer - please
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