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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 01-27-2006, 11:19 PM
bimmer328_97 bimmer328_97 is offline
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Mein Auto: 328is 1997
Catalytic Converter Failure

I am in emissions hell. Got a check engine light, went to dealer and he said I needed to replace O2 sensor. Replaced O2 sensor and check engine light came back on again. Got reading for codes and found out that other O2 sensor was reading fault, and then biggest bummer, catalytic converter below efficiency.

My question is this, is it possible to get a false catalytic convertor code if the oxygen sensor needs to be replaced. Should I go ahead and replace both the catalytic converter and the oxygen sensor or should I first just change the faulty O2, reset the check engine and then wait to see if catalytic converter failure is for real.

Any input would be greatly appreciated.

Thanks!
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  #2  
Old 09-08-2006, 07:43 AM
Playboy628 Playboy628 is offline
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I don't know the exact answer to your question but this might help a bit. I had my cat go out on my 97 528i and ordered a new cat off the internet for around $300. A mechanic installed it but I had no idea that I was supposed to replace the O2 sensors with the cat. Around a month later my check engine light came on and my dealership said that the cat failed. This was because I did not replace the O2's with the cat. I left my check engine light on for around a month and it eventually went out and has not come back on for several thousand miles. The car has run fine ever since I had the $300 aftermarket cat installed. From everything I know, you should replace both otherwise you could get blow your dow on the O2's and have them go out shortly after installation. You can get aftermarket cats off the net for around $300 that have a warranty and then have a local mechanic install it for much cheaper than a dealership. Thats what I had done and this has worked out good for me although I regret not having the replaced with the cat. Hope this helps.
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  #3  
Old 09-08-2006, 10:11 AM
lesl2 lesl2 is offline
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Mein Auto: '97 & '99 M3, '02 530
O2 sensors are $110-$200 each, depending on where you purchase them. And, you need 4 of them. If I were you, I'd would monitor each sensor via the OBDII port and replace just the one that is malfunctioning. If you see that all are functioning properly, go for the cat. I see that you are in NJ. For others like me in CA, we have to do more troubleshooting. A cat in CA costs >$1700 because you cannot use an aftermarket cat in CA on OBDII vehicles.

I had an emission issue, high NO. All the mechanics said to replace the cat. Did research on the net and found that the cat does not function properly if your engine is running hot. I found via the OBDII port that my coolant temp was actually at 220-230 degrees. Temp gauge on the dash is digitally buffered. Stays at 12 o'clock between 180-235 degrees. I fixed the coolant problem and the NO went way down. I finally passed my CA emissions requirement.

I use this on the OBDII port: http://www.obdscan.net/obdscan+can.html
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Last edited by lesl2; 09-08-2006 at 10:14 AM.
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  #4  
Old 04-12-2008, 07:52 PM
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dtvarnum dtvarnum is offline
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Quote:
Originally Posted by lesl2 View Post
O2 sensors are $110-$200 each, depending on where you purchase them. And, you need 4 of them. If I were you, I'd would monitor each sensor via the OBDII port and replace just the one that is malfunctioning. If you see that all are functioning properly, go for the cat. I see that you are in NJ. For others like me in CA, we have to do more troubleshooting. A cat in CA costs >$1700 because you cannot use an aftermarket cat in CA on OBDII vehicles.

I had an emission issue, high NO. All the mechanics said to replace the cat. Did research on the net and found that the cat does not function properly if your engine is running hot. I found via the OBDII port that my coolant temp was actually at 220-230 degrees. Temp gauge on the dash is digitally buffered. Stays at 12 o'clock between 180-235 degrees. I fixed the coolant problem and the NO went way down. I finally passed my CA emissions requirement.

I use this on the OBDII port: http://www.obdscan.net/obdscan+can.html
Hi, I am in Anaheim, Ca. I did not pass smog yesterday. My Indy says cat is bad. I asked him this 3 weeks ago when he put a head in. He said oh now not the cat, well now he says is the cat. I tend to not believe him since his tech told me they couldn't OBDII my car computer when I asked him why the ASC light and the airbag light was on. I wonder how he knows it's the cat if he can't read the computer?

Well I plan to go to my old indy shop and get a good read. Where did you get your cat? Do I need to buy two and 4 sensors? I have a 528i MY97 220k miles.
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  #5  
Old 12-23-2008, 09:28 AM
itoth itoth is offline
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Mein Auto: 1998 BMW 540i
Just yesterday, I was able to smog my car. Thank God!

I had the "Check Engine" light on and when we checked it, it showed catalytic bank 1 & 2 were bad.

To change both of them, I have checked with local shops and bmw, and gotten prices from $950 - $3,400.

I was also told, after market or universal catalytic converters might not do the job and the "check engine" light will come back again, after I drive the car from anywhere 30-100 miles.

So with this information and knowing I could not afford even $950, I gave it a chance to take it to a local muffler shop. In 30 minutes, they cut and welded back two new CA spec. universal ones (Magnaflow 46005). I paid $700 total. Here is the webside for the same one I purchased and was installed (the muffler shop had this in stock so I did not buy them from this website);

http://www.******************.com/fe...461468688.html

After the installation, I went to another shop and they took the "check engine" light off (for free) and I drove the car for almost 90 miles before I took it to the smog station. It passed the test in a few minutes and the light has not come back. I hope it will stay so.

My bmw has already 210,000 miles and I newly purchased it from a friend and it still runs very nice. I was going to keep it on my friends name if we could not smog but all turned out to be for the better, thank God again.

Well here is my story and I hope I was able to help some of you with my feedback.
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  #6  
Old 12-23-2008, 06:18 PM
BadgelessM3 BadgelessM3 is offline
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How many 02 sensors did you change? Becuase the e36 m3 has 4 of them only change 1 will not help
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  #7  
Old 12-29-2008, 08:51 AM
itoth itoth is offline
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I did not have to change the 02 sensors. By the way, the 1998 540i has 4 O2 sensors as well and it is easy to change as I have read it.

Also, as an update, since I changed the catalytic converters, I am getting incredible mileage. I took the car two days ago for a 3 hours trip and zerod (cleared the "consumption" reading) just at my house. On the way there, I got a reading anywhere from 9.8 - 10.4 but I was driving uphill for about 100 miles.

On the way back, it went back down to 9.3 l/km (liters per km) that is 30.3 miles/gallon. Incredible and it stayed so even when traffic slowed down (happened often) due to heavy traffic.

The BMW manual says that the car gets anywhere from 245-27 miles/gallon but mine has gotten much better and so I have read from others who experienced the same, after changing the catalytic converter(s).

So if and when needed, I suggest to change the catalytic converter as it will perform better and save much gas too.

My experience, O2 sensors do not need to be changed when changing the catalytic converter(s).
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  #8  
Old 12-29-2008, 03:13 PM
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drivinfaster drivinfaster is offline
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you can use aftermarket cats on any vehicle, obd2 or not. the fit and finish may not be all that great, as they vary by manufacturer, but rule of thumb is a cat for a bmw is not going to cost 69.95. also, they are directional, and you can have them put in backwards. this will usually be reflected in a NOx failure.

and the post cat o2 sensor is the one that is used to check the efficiency of the cat. the pre cat sensors do not always need to be changed if they are functioning properly. a good shop with a 4 gas reader will be able to verify the catalyst efficiency (the ability to reduce the hc & co into co2 & h2o), as well as the ability of the cat to retain oxygen. a cat that has been run rich and coated with carbon *can* fail this test, even though the cat is nowhere near the age of expectancy for failure. the standard proceedure for a cat failure at our shop was to verify both the catalyst & retention readings, run some fuel system cleaner through and retest. if the readings improved, then happy joy, mr customer has bought some time. if the readings did not improve, well then you just verified the diagnosis and ensured the existing buildup will not run the risk of shortening the life expectancy of the new cat.

and then generally yes, we suggested rear o2 sensors simply because most times there was no additional labor to install them and there was no way that we could guarantee they wouldn't be seized in the threads and get damaged upon removal. not because it would void any warranty or anything like that. very dangerous, thin ice to make that statement simply because if the sensor that says my cat is bad must be replaced in order to insure the new cat is good. how did this sensor determine the condition of the cat accurately, if the reliability is so questionable that it won't survive the new cat?? (and no, a post cat o2 will not in any way, shape, form, or scenario possible in this world or the next, ever kill a cat. period amen. no way. no how. never ever saw it.)

df

Last edited by drivinfaster; 12-29-2008 at 03:15 PM. Reason: miss-spelled woordz
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  #9  
Old 01-09-2012, 03:37 AM
EZBREEZY EZBREEZY is offline
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Mein Auto: 1998 M3
I too am in catalytic converter hell. My 1998 M3 convertible coupe that failed inspection. Dealer quote (with car unseen), $3200, including parts and labor. Hell that's half as much as the car is worth. Don't get me wrong, I love my but sounds like a rip off, when the part (I checked on in parts department first), is only $300 dollars. You're charging 10 times more than the cost of the part, sounds like plumbers hours to me. Went to a second BMW repair shop and I was told it may just need to be blown out first, cost $165. They would try that first...by the way the engine lights on....goes on and off. No other messages. Smell of oil or fumes do smell insude, knee area on drivers side and the radio is hot even with heat off. How do you know who to believe? 3rd body shop said, "it could be your 02 sensors". Trying to get a proper reading and answer and not get taken. The later, two sources did place car on diagnosis machine. Each gave a different reading. Dealership "guess-timated". What harm is done to myself safety wise a.d then to the car, if undone or held off a while? The second place by the way will not do aftermarket parts, which they quoted me $1600-$3200. Aftermarket-market parts.
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  #10  
Old 01-09-2012, 07:59 AM
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drivinfaster drivinfaster is offline
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wow....talk about a blast from teh past...

first, your vehicle should have a code for cat efficiency stored, along with freeze frame data. get this information.

second, the cat should be tested with a gas analyzer. no need to do NOx testing (done on a dyno only, no other way to get accurate readings) unless your state tests for it. it is not monitored on the cat efficiency test.

what is monitored on a self test are the results from 2 tests. one is a reduction efficiency test, the other is an o2 retention test. a competant shop will run these prior to replacing the cat.

bottom line, the computer is blind and goes by what it 'sees'. it looks at the rear o2 for this information. if the rear o2 sensor either mirrors the primary sensor (not a good thing), then the cat is dead. the secondary o2 could be faulty, so it, too, should be verified.

the rear o2 *only*, i repeat, *only* checks the cat. it has no bearing on the driveability of the vehicle.

the cat is not too difficult to replace, if you go with an oe or direct fit unit. there are lots of them out there, but they are a bit pricey.

you'll need tools, jackstands (unless you have access to a lift), a torch (to heat the exhaust nuts), new hardware (suggest copper nuts), and gaskets.

you may also wish to invest in a new hanger as well. they tend to get all bent up or break when they don't come off easily.





df
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  #11  
Old 04-08-2013, 01:14 PM
KyleBrown KyleBrown is offline
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Hi Itoth,

I see you are in San Francisco? I know it was an old post but can you tell me the name of the muffler shop. My indy mechanic quoted me $3k to replace both cats. And I am looking for other options for the same issue. I see aftermarket cats at rock auto for $300 but not legal to sell in California. I replaced the front 02 sensors awhile back. Also I just passed smog running green sky fuel additive which turned off my service engine soon light. It is back on though when not using the additive.

Thanks for any help




Quote:
Originally Posted by itoth View Post
Just yesterday, I was able to smog my car. Thank God!

I had the "Check Engine" light on and when we checked it, it showed catalytic bank 1 & 2 were bad.

To change both of them, I have checked with local shops and bmw, and gotten prices from $950 - $3,400.

I was also told, after market or universal catalytic converters might not do the job and the "check engine" light will come back again, after I drive the car from anywhere 30-100 miles.

So with this information and knowing I could not afford even $950, I gave it a chance to take it to a local muffler shop. In 30 minutes, they cut and welded back two new CA spec. universal ones (Magnaflow 46005). I paid $700 total. Here is the webside for the same one I purchased and was installed (the muffler shop had this in stock so I did not buy them from this website);

http://www.******************.com/fe...461468688.html

After the installation, I went to another shop and they took the "check engine" light off (for free) and I drove the car for almost 90 miles before I took it to the smog station. It passed the test in a few minutes and the light has not come back. I hope it will stay so.

My bmw has already 210,000 miles and I newly purchased it from a friend and it still runs very nice. I was going to keep it on my friends name if we could not smog but all turned out to be for the better, thank God again.

Well here is my story and I hope I was able to help some of you with my feedback.
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  #12  
Old 05-14-2013, 07:06 PM
thomastuck11 thomastuck11 is offline
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Ok, my turn. Last August I replaced both catalytic converters on my 1998 e39 540i due to the "death rattle". Recently I've been getting repeated catalytic converter efficiency faults (on both banks) when I'm in bumper to bumper traffic, or if I sit idling for a long time (like in a fast food drive through). I first replaced both upstream sensors and the check engine light came back on shortly thereafter for the same fault. Next I replaced both of the downstream sensors and the COL came back on again (still same fault). My mechanic thinks the catalytic converters are too small and are cooling down during periods when the engine isn't producing a lot of hot exhaust, and consequently the efficiency of the converters drops off. Has anyone had similar problems?
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Old 05-14-2013, 07:54 PM
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drivinfaster drivinfaster is offline
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while this is an e36 subforum, i can assure you that the pcm looks at cat efficiency the same way on all obd2 cars. it reads the post cat sensor for input. that's all this sensor does, monitor the cat.

now, does the mechanic you talked to have a gas analyser?? if not, then find another shop to test the cat. if the shop cannot read the gases coming out of the pipe, then there is no sense in having them take a look at anything.

they should also have a dual trace scope of some sort that can take a live reading of both the 2 sensors on a givenbank to compare the signals. they should be different. the pre cat should cycle up and down, while the post cat should be mid to high with little wave.

a cat can fail its efficiency reading by either not being able to retain free oxygen, or, not be able to reduce the hc and co properly.

depending on the size of the cats, and who made them, condition of the vehicle, and whatnot, they could either have been too small of a replacement (probably much cheaper as well....), or, were killed by what killed the original cats....


hope this helps.



df
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Old 05-14-2013, 09:26 PM
thomastuck11 thomastuck11 is offline
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My apologies, I was searching the forums and posted to this one before I noticed it was foe E36's. I'm stopping by my mechanic tomorrow morning, but I suspect he doesn't have a gas analyzer. This car only has 104k miles (not bad for a 1998) and has been through three (3) sets of catalytic converters since 2008! I need to stop treating the symptoms and find the real cause of this issue.
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Old 05-15-2013, 05:51 PM
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drivinfaster drivinfaster is offline
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whoa!!!! that's insane!!! yeah, sounds like someone isn't doing something correctly somewhere. there's no way a cat should go bad that fast unless you're using the wrong type of fuel (ie, leaded....) or running super rich. (in which case, i would suspect that rich codes would be popping up....)

check the fuel trim status. if it's running negative, that indicates additional fuel entering into the engine unmetered (evap system, leaky injectors, malfunctioning fuel pump)

any mods?? (oversized injectors, tune,...that sort of thing??)

also, check the maf. a poorly functioning maf will trigger all sorts of stupid codes, and, maybe, trigger something like this. do you get a lot of o2 sensor codes as well??




df
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Old 05-15-2013, 06:12 PM
thomastuck11 thomastuck11 is offline
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The only codes are for right and left bank cat efficiency, no other codes have appeared. The cats are AP608214 (left) and AP608215 (right). I spoke the the guy who installed them and we figured out that these aren't the recommended cats so now I'm looking into installing AP608235 or AP608265 (OBDII) cats.

The exhaust guy was very apologetic and is going to credit the cost of the old cats towards the new cats. I asked about Magnaflow cats and he indicated that he won't install them anymore due to a lot (dozens) of failures. He stated Magnaflow makes terrific mufflers, but lousy cats.

I should mention this car has a Dinan cold air intake with larger throttle body and stage II engine tuning software. It also has the Dinan freeflow exhaust system. The exhaust guy thinks the tuning software runs the fuel trim a little richer at low RPM which may contribute a little bit to the problem.
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Old 05-18-2013, 07:11 AM
thomastuck11 thomastuck11 is offline
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Having new cats installed this morning. Going with AP Exhaust Technologies 608235 converters. Wish me luck.
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  #18  
Old 06-21-2014, 10:09 AM
gmak2012 gmak2012 is offline
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Does the death rattle sound like a woodpecker kind of.

Quote:
Originally Posted by thomastuck11 View Post
Ok, my turn. Last August I replaced both catalytic converters on my 1998 e39 540i due to the "death rattle". Recently I've been getting repeated catalytic converter efficiency faults (on both banks) when I'm in bumper to bumper traffic, or if I sit idling for a long time (like in a fast food drive through). I first replaced both upstream sensors and the check engine light came back on shortly thereafter for the same fault. Next I replaced both of the downstream sensors and the COL came back on again (still same fault). My mechanic thinks the catalytic converters are too small and are cooling down during periods when the engine isn't producing a lot of hot exhaust, and consequently the efficiency of the converters drops off. Has anyone had similar problems?
Sorry to respond to an E39 post on an E36 forum, but from time to time I hear a sound from my car (usually while at idle, after driving for a while) - but sometimes while driving - that sound like a woodpecker for about 5 seconds or so. Then it stops. the sound comes back from time to time. Is this the "death rattle"?

Cheers.
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Old 06-21-2014, 05:54 PM
thomastuck11 thomastuck11 is offline
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The death rattle noise results from shattered matrix inside the catalytic converters. 2 man job: You need to get close to the converters while someone revs the engine to see if they're the source of your noise.
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  #20  
Old 06-22-2014, 07:13 AM
gmak2012 gmak2012 is offline
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Thanks.

Thanks. I'll check it out. The problem I have is quite intermittent and always seems to stop before I have a chance to check it out. I should be thankful, I guess that it's not the full on death rattle as seen on youtube.
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