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-   -   CA Smog Check Fail - Fixes? (http://www.unitedbimmer.com/forums/showthread.php?t=56972)

foaxaca 10-31-2012 10:53 PM

CA Smog Check Fail - Fixes?
 
My daughters 1996 328is just failed California smog check. Here are the numbers:

HC (PPM) NO (PPM)
MAX AVE MEAS MAX AVE MEAS
15 mph 54 9 78 430 67 446
25 mph 37 6 37 717 62 192

Basically failed at 15 mph for HC and NO. Going to start by changing out O2 sensors and plugs. Just changed oil a week ago. No CEL codes. Any other suggestions?

Manolito 11-01-2012 12:09 AM

Make sure that it is fully warmed up when you pull it in the shop. The hotter your catalyst is, the better it works.

DEATH2000 11-01-2012 12:33 AM

Hit the Cat. If it sounds all "junky" then its probably bad.

foaxaca 11-01-2012 09:54 AM

Hoping it is not a bad cat since that sounds expensive to deal with. Someone else suggested looking at the EGR system for buildup. Any idea how to take care of that?

foaxaca 11-02-2012 02:02 PM

I'm shopping for new O2 sensors and getting some confusing info. How many does this car (1996 328is) have? 2 or 4? Are they both connected to the exhaust manifold or to the catalytic converter? Or is it one in each location? Thanks!

DEATH2000 11-02-2012 02:10 PM

OBDII cars (post-1996) have one pre cat sensor and one post cat sensor.

foaxaca 11-02-2012 02:17 PM

Mine is a 12/1995 build, 1996 model. Is it OBDII as well? It has the older round diagnostic connector I use to plug my Peake reset tool to read error codes and reset CEL, oil change and inspection lights.

DEATH2000 11-02-2012 02:31 PM

Anything build for 1996+ is OBDII.

Manolito 11-02-2012 11:56 PM

Your 1996 OBD II car requires four oxygen sensors.

The front ones are screwed into the exhaust manifold just above where it connects to the exhaust pipe. Part number is 11781437943

The rear ones screw into rear of the catalytic converter. Part number is 11781427884.

You don't need a special oxygen sensor socket. In fact, the special socket won't fit in the space on this car. A combination wrench works great. Be very careful not to cross the wires. Best to replace them one at a time to ensure that you don't cross any wires.

BMW's recommended replacement interval is 90k miles. If your oxygen sensors have over 100k miles on them and the computer is storing a code "catalyst below specifications", you need oxygen sensors. I always replace all four at once. I trust NGK (I think they label their sensors NTK) or Denso for oxygen sensors, and I don't use the generic sensors that you have to crimp onto your electrical leads.

foaxaca 11-11-2012 10:29 PM

Here's the latest... Changed out spark plugs, replaced with Bosch Platinum +4's and replaced pre-cat O2 sensors with Walker Products replacements. Drove the car about 1/3 mile to local Chevron station, filled it up with 91 octane and added a can of SeaFoam to the gas tank. Car ran smoothly getting there. Left the station and pushed it up to around 60 and before I got back home, stopped at a light and noticed that it was idling roughly and below it's normal idling RPM's. Just as I was making the final turn into my street, CEL came on. Damn! Pulled it into the garage, pulled out my Peake tool and read several O2 sensor adaptation and control limit and cylinder misfire codes. I'm thinking if these were the wrong O2 sensors I would have noticed something right away. I triple checked the part number to make sure these were the correct replacements. Is there some re-adaptation that needs to take place when you change out O2 sensors that may cause error codes before that happens? Cleared the codes and re-started the car and it ran smoothly and no CEL. Didn't run it on the street though. Any hints?

foaxaca 11-12-2012 11:40 AM

Bonehead Maneuver!!
 
Embarassed to admit that after reading another post and looking in the Bentley manual it suddenly occurred to me that I may have flipped the leads for the O2 sensors and plugged them in backwards. Sure enough, switched them and the car idles perfectly. Will still change out the old plugs with identical replacements and forget the +4's for now based on what other posters are telling me.

Manolito 11-12-2012 09:48 PM

The spark plug manufacturers tell us that +4 plugs should work fine in e36s, but most of us have tried them through the years and have gone back to two electrode plugs, which was what this car came with. I cannot explain why a two electrode plug could possibly work better than a four, but they seem to. I tried four electrode plugs in my old Volvo once, and was less than impressed with them in that car as well.

The e46s came with four electrode plugs, and that is what we use in e46s, which makes this mystery even more inexplicable.

If you have a fresh set of +4s in the car and they seem to work fine, I would use them and get my money's worth if it were my car.

foaxaca 11-17-2012 11:56 AM

Decided that it wasn't a fair test to try the +4 plugs with the pre-cat O2 sensor leads reversed. Switched the leads and reinstalled the +4's this morning and the car started, reached proper idle and ran fantastic. No misfires, no CEL and great power. Smooth and strong acceleration. I'm going to leave them in. Is it safe to assume that if I am not getting any post-cat O2 sensor codes, I shouldn't worry about changing them out also? Have about 3/4 tank of fuel with SeaFoam in it I have to finish off so I have some time left before retesting.

DLL66 11-17-2012 12:24 PM

Quote:

Originally Posted by foaxaca (Post 222165)
Decided that it wasn't a fair test to try the +4 plugs with the pre-cat O2 sensor leads reversed. Switched the leads and reinstalled the +4's this morning and the car started, reached proper idle and ran fantastic. No misfires, no CEL and great power. Smooth and strong acceleration. I'm going to leave them in. Is it safe to assume that if I am not getting any post-cat O2 sensor codes, I shouldn't worry about changing them out also? Have about 3/4 tank of fuel with SeaFoam in it I have to finish off so I have some time left before retesting.

My opinion is to leave them in there if you're not experiencing any problems. You bought some pricey spark plugs, it be ashame to throw them out at this point.

Manolito 11-18-2012 10:24 AM

In any car, the rear oxygen sensors last longer than the front oxygen sensors, so it is common to replace them at different intervals. The owners manual, however, suggests changing all four at 90k miles.

Knowing that the sensors get slower with age, I like the idea of having a matching set, so I do all four at once.

That being said, if the car is running great and not throwing any codes, there is a strong argument for "if it ain't broke, don't fix it..."


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