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Need Help Passing a Smog Test in SoCal


Jack_K

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Hi All,

 

I own a 1976 BMW 2002, which means it’s subject to passing the dreaded smog test every other year when I renew the registration. (1975 was the cut-off date for being grandfathered in here in California.) Long story short, I’ve owned the car for about ten years and have managed to get it to pass my smog every time.  

 

This time, despite my very good and trustworthy mechanic’s best efforts, he was unable to get it to pass the test.  He thinks the problem is too many adjustments to the carburetor since the last test, as well as normal wear and tear on the smog components i.e. thermal reactor. 

 

He gave me the name of a guy in Highland Park that rebuilds carburetors, but I thought I’d reach out to the board to see if anyone has or knows of a mechanic who knows his way around the smog equipment on a 1976 BMW 2002 or who specializes in 2002’s.  Or if anyone has any tips or suggestions on how to get a car to pass a smog test here in California.  I’m open to any and all suggestions.  Thanks very much!

 

-Jack
 

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You mentioned the thermal reactor on your car, so it must be a California Spec '76.

Can you share the smog test numbers that are causing your car to flunk?

The smog guys are supposed to conduct a visual check to make sure smog equipment is present (but not necessarily functional).

Most don't know what they are looking at...just trying to check off stuff in their manuals.

Then a tail pipe sniff test to see if the HC, CO and NO are under the max allowable. 

I've owned my CA '76 for 47 years and have been dealing with the CA smog tests since they became mandatory in 1986.

Hope I can help ... we are brave souls indeed!

John

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Hi John!

 

Thanks for replying so quickly.  Yes, I have the numbers from the original test.  My mechanic tried it a couple more times unofficially on a friend's smog tester, but I don't have those numbers.

 

I've attached the results from the first test.  

 

IMG_6382jpg.jpg

IMG_6383jpg.jpg

Edited by Jack_K
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...and too little fuel.   Try raising the carb float just a little bit...

 

The oxygen in your tailpipe is probably unburnt, as there's not enough fuel to use it all.

The very low HC supports that.  

 

hth

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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Your combustion gasses (CO2 & O2) look good.

HC and CO are also fine. 

The high NO levels are most likely due to a plugged EGR filter or a clogged 2-stage EGR control valve.

Both can be cleaned enough to pass.

John

BTW: I flunked a test due to old gas (10-months old) which sent the 15mph HC through the roof. 

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With high NOx, you can also get away with retarding the timing a bit. This will raise the other values, just need to find the sweet spot where it's all under the threshold. But cleaning the EGR system is a better place to start. 

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'68 Caribe 1600-1563167

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4 hours ago, John76 said:

Your combustion gasses (CO2 & O2) look good.

HC and CO are also fine. 

The high NO levels are most likely due to a plugged EGR filter or a clogged 2-stage EGR control valve.

Both can be cleaned enough to pass.

John

BTW: I flunked a test due to old gas (10-months old) which sent the 15mph HC through the roof. 

 

Thanks, John!  I will give this a try.  And that's good to know about old gas.  My tank was nearly empty and definitely had some old gas in it when my car was tested.

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6 hours ago, Mark92131 said:

Any tricks for cleaning the filter?

It's loaded with carbon soot. It's a messy job, but easy.

I tap and shake it, then vacuum both ends with a shop-vac.  Finish with a blast of compressed air.

For the 2-stage EGR valve use carb cleaner, brushes and picks to clean the crud off the valve seat and plunger.

Test the diaphragm for leaks with a vac source. Stage 1 is connected to ported vacuum and opens the valve a small amount to recirculate exhaust only at partial throttle for the 15 and 25mph test.

8 hours ago, FunElan said:

With high NOx, you can also get away with retarding the timing a bit.

Yep...car will run like %$#@, but set the "BB" @ 2500 rpm (min) to pass the test.

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I’m not an expert on this but years ago there was a thing called a nox device that made the car run badly but reduced NO emissions

after the car passed I removed it. I think it limited the timing advance so that would agree with the above post

good luck

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35 minutes ago, 2ma2 said:

a thing called a nox device

The '75 and CA '76 cars had a coolant temperature switch controlled EGR relay that would turn off vacuum advance when the engine reached operating temperature (coolant > 150 deg. F). The vacuum retard pod on the distributor lowered the NOx but made the car run poorly. The '76 49-state cars were more creative...the ditched the EGR completely in favor of a different camshaft that kept the exhaust valve open a bit longer and increased the lift on the intake valve to dilute the incoming charge. This "cooled" the combustion temp enough to lower NOx without retarding the spark.  Anyone have a spare #5 camshaft??

 

BMW2002EmissionControls76CA.thumb.jpg.0430aa6c25636e6a77ca5b076c9d1d9c.jpg

 

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Please Google: Isopropyl (closest to 100%) or denatured Alcohol to lower NOx. 


I have used this twice in cars (Honda Passport and an e39 touring) that had previously failed NOx levels. 


IIRC, I added about a 1/4 cup isopropyl to the tank full plus added Lucas octane booster for good measure. 

Run the car for at least a quarter tank, then off to your smog appointment. 

This I do for every car I smog: Fresh oil change. Make sure your engine is hot (having A/C on helps). Keep it running right up until they ask you for the keys. Squirm like you are waiting for the doctor to put on the nitrile gloves and give you the I’m sorry look.
 

When she passes the smog check, play the Lotto 😄

Edited by RichenFamous
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Well, judging from the CO% yer running lean, way lean.

I don't know what the emissions targets are for '76 and can no longer speak to carburetor tuning, but not a fan of adding alcohol to CA gas as it's already up to 15% . My solution was always use 100 octane race gas to slow down the combustion. It worked very well for me on the Turbo and Tii.

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39 minutes ago, Einspritz said:

Well, judging from the CO% yer running lean, way lean.

I don't know what the emissions targets are for '76 and can no longer speak to carburetor tuning, but not a fan of adding alcohol to CA gas as it's already up to 15% . My solution was always use 100 octane race gas to slow down the combustion. It worked very well for me on the Turbo and Tii.

 

It was my understanding that slowing combustion will increase temps, therefore NOx? My last e36 smog check, I used low octane fuel for two tanks (I know) to lower NOx and it helped. The ECU retarded the timing and I passed. 

'68 Caribe 1600-1563167

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