E36 92 325i high nox smog issue please help - United Bimmer Community

**luciddreamer** · 02-19-2010, 08:01 PM

Hi,
I desperatley need some help !!! Especially since I'm a single gal with no mechanic in the family.
My car is a 1992 325i

I took it in to be smogged it failed as a gross polluter with extremely high nox measuring at 2037 and high hc measuring 226 at 15 ppm

I took my car to a european auto repair ( not a smog repair station) in my town and had a dagnostic run. he called and told me my 02 sensor was bad and this is why it was failing so I had him replace it. I also had the oil changed and new spark plugs. I took it back to smog and low and behold the numbers were the same and it failed again. I called him to tell him and he said the sensor was bad but I must also be needeing a catalytic converter and refered me to another shop to get that replaced. I had a new cat put on and took it back to smog, well it still failed however the new numbers were much better it passed in every area except the nox at 15mph. it did pass the nox at 25 but not at 15. The new nox numbers after the cat was installed are still high but lowered down to 1090 at 15ppm The car runs great has lots of power, get's great gas mileage of 26-27 miles a gallon and does not burn oil. Can anyone help me with what might be wrong, I am now scared to take it back to him as I have already spent a whole lot of money and it still won't pass as well as I am a bit concerned that the original diagnosis of an 02 sensor was not what was wrong with the car and did not even change the numbers.. Please help I am feeling very desperate and afraid to just take it back to the local repair shop.
Please help!!
Thank you,
Lorie

**luciddreamer** · 02-22-2010, 08:35 AM

Here is an update !! I was told to try some stuff in the gas tank called Lucas to help with excessive carbon build-up. Well it really helped, it almost brought the nox level to passing but not quite. I live in California and the max nox is 785 I am now at 938

does anyone know of a fairly inexpensive way to get the excessive carbon buildup down. I am nearly out of money available to spend on the car. I have already spent over 1,500.00 trying to get it to pass smog

**luciddreamer** · 02-23-2010, 09:47 AM

Hmmm I don't know what to think !! Lots od views and zero replies. Does anyone want to buy my car ?? I've exhausted my money supply and need to get rid of it so I can buy something I can drive !! registration is now expired and I can't get it to pass. I will also consider parting it out. I live near Sacramneto CA

user1 · 02-25-2010, 02:33 AM

damn that really blows.
no one locally you can turn to for help or advice on the smog?

**David Mc** · 02-27-2010, 12:28 AM

Okay, this dates back to when engines were cast iron lumps with ginormous carburettors. The easiest way to remove carbon was to find a long, steep hill. Start at the bottom and use the highest gear practical (i.e. one that puts the engine under load without causing it to strain badly), accelerate hard, taking the revs right up before changing up and repeating the procedure. Basically you are trying to increase the combustion chamber temperature and burn the carbon out. Since this is a BMW make sure to watch that your temperature gauge or you may wind up with more problems than a carbon build up. Blasting along the freeway for a couple of hundred miles is good too, but I think the speed you would need to achieve in a Bimmer may result in you punching out license plates if you get caught.

**David Mc** · 02-27-2010, 07:26 PM

Here are a few other ideas http://www.rollaclub.com/faq/index.p.../Decarbonising - I would advise against the water method, which is really only suitable for carbed engines as it is highly likely damage sensors in your BMW's intake system.

**luciddreamer** · 03-01-2010, 03:02 PM

Here is the latest. I ran the Lucas additive through and had a smog pre-test done. It shows that the numbers are fluctuating and surging, it will get below thae allowed numbers for passing but will only stay there for about 3 or 4 seconds and then it surges back up t the not passing mark. of course 3 or 4 seconds is not long enough to pass the test. Does anyone have any ideas ??? PLEASE HELP !! as i was before it is passing at the 25 rpm mark but not the 15 rpm mark

**David Mc** · 03-01-2010, 04:28 PM

Lorie,
Firstly, you do not need to pay for a diagnostic, this will explain how to do it yourself (without tools) http://www.pelicanparts.com/BMW/tech...de_Reading.htm . If the Lucas product is a fuel injection system cleaner that you have run through the car by adding to the fuel tank, this is a good move (I am not familiar with this product, which may not be available here). After the O2 sensor was changed and the new cat was installed, did the mechanic re-set your car's adaptation values? This is information stored in your car's DME, which tailors your fuel trim values, based on your driving style, engine condition and load. If not, nothing would have changed in terms of the emissions in the short term, as the car would have still been using fuel trim settings stored whilst the components were defective. Anyone with Carsoft, DIS/GT1 or INPA diagnostic software can re-set adaptation values for you in about 5 minutes. You will need to drive the car under a variety of load conditions for up to 2 hours after this has been done, so that your car can re-learn and set correct trim values. Make sure that some of the drive cycle that you do includes low load, stop-start driving at under 15mph so this information is also included. Finally, take the car for a blast along the highway to clear any remaining carbon deposits and you should then have your best shot at passing the emissions test.

**luciddreamer** · 03-09-2010, 12:21 PM

Update #2 brought car to another european shop. They found the mass air intake boot ws cracked, said it was the problem and would cause the high nox reading at 15 mph. I had them replace it and lo and behold it still fails smog but jut barely fails as it was before the boot. So there was another 225.00 for a total of almost 1800.00 into it and it won't pass smog still. Te mechanic stated it is running great and passing all dignostics. Any body have any other ideas ???? I am just devastated !!

**David Mc** · 03-16-2010, 03:18 PM

OK, delving into the causes of high NOX emissions, they result from high engine combustion temperatures arising due to:-
Dirty fuel injectors
Clogged fuel filter or low fuel pump output
Intake manifold vacuum leaks after the MAF
Dead Cat Convertor
Lean fuel mixture
Advanced ignition timing.

Of all the above, retarding the ignition timing by a couple of degrees probably has the biggest effect on reducing NOX emissions. I don't know how much you are failing the smog test by, but based on your previous posts it can't be much. Rather than attempting to diagnose the problem without seeing the car or leaving you to the mercy of your dealer, I figure if I give you the basics, you should be able to eliminate the stuff you have done and concentrate on what has not been looked at without getting ripped off.

**M3RACR** · 04-06-2010, 08:32 AM

Hey, I had the same problem with my 1995 M3. Buy some RXP (small, orange bottle) at your local autozone and add it to your gas tank (half full). The lucas isn't any good. Drive around for 50 miles, then take your car directly to the emissions place, it should barely pass. Make sure to really open up the throttle for a good stretch as well. Good Luck, I'm about to go do the same (my tag expired in March). Cheers

**C Sean Watts** · 04-06-2010, 09:04 AM

are well known to run lean, causing high combustion temps and high NOx. In turn, this causes cat and O2 sensor problems. It's all downhill from there.

Change your fuel filters every 12 months/12,000 miles and no more. Also, pouring in your favorite flavor of "mechanic in a bottle" does NOT get the injectors clean enough. You'll need to take them out and have them run through an ultrasonic back flusher. Reputable shops do this about $20 each and will send you a print out of before and after flow tests. OR you could buy the ~$2000 machine and DIY.

**luciddreamer** · 04-17-2010, 01:08 PM

I know this is late in updating but we got the problem fixed. To our amazmant the issue was the shop that installrd the cat did not weld it properly and there was a leak in the weld. We took it to another shop that repaces the mas air intke boot as he said it was cracked, it still did not change the numbers ater that he figured out it was the weld in the cat, took it bck to the mufler shop they re-welded and walla it passed with flyng colors.

**David Mc** · 04-17-2010, 03:51 PM

Good news, congrats.

**gc325is** · 05-01-2010, 01:00 AM

FYI CA wants to help you pass smog. They offer a $500 assistance to perform all the things you did. No income limit just sign up and go to a gold standard repair shop. You may also need to test at a test only shop.

My NO levels were only a few 100 over and all it took was the tester let the car warm up 10 min before the test. (I also ran it for 30 min). He said need a hot Cat for BMWs to pass. Other pre test items are new plugs, check for Vacuum leaks, injector cleaner and Seafoam cylinders for carbon.