Failed smog test

I think I was too lazy. Without doing anything I went to a smog checking station and it failed because of hi NO and HC.

15mph 25mph
%CO2 14.9 15.0
%O2 0.2 0.0
HC 127/81 39/40
CO 0.27/0.47 0.07/0.30
NO 721/478 131/484

It seems fine in 25mph but failed in 15mph. I should start researching what I need to do to reduce HC&NO in low speed.

My 93 has been diagnosed with having a bad knock sensor. And not passing smog Supposedly this is making it not burn all the gasoline .I have tried nearly everything else.I have two knock sensors coming anyday now .Ill let you know if it works.. Once i found one of the sensors had come unplugged at the end of a long trip. It never was the same again. Funny Calif laws ,if i move 25 miles away uphill the towns are smog exempt.

Actually I was able to smell bad gas when I start driving. I wonder if this could be because of vacuum leak. However it seems fine in 25mph. I wonder if vacuum leak should cause consistent failure in 15mph and 25mph. Thanks for the info. Let me know how your try goes.

I found pretty good threads for this issue. They seem very useful.
http://www.bimmerfest.com/forums/sho...d.php?t=655347
http://www.bimmerfest.com/forums/sho...d.php?t=648574

Yes those are good links on subject. Ill be trying everything to save Tanja-93 in the next quarter .I Just had the one o2 sensor replaced ,and now replacing 2 knock sensors .

While replacing an air filter I found a few issues in air hose. There are a couple of cracks. One of them is huge ! I believe it has been a while and the car was driven with the cracked air hose. I'm wondering if this caused contaminated engine oil cap area. When I replace engine oil the cap and area where I pour engine oil is pretty dirty with dirts. I'm guessing the crack sucked all the dirt without air filter and contaminated the engine. I don't know how bad this could be but let me know if I there is some area where I look at which could be troubled with this crack. After fixing these hoses, I will go to the emission test again to see if this was the cause.

Yup, replace that hose and change the oil.

Bet it'll idle better too

I replaced the cracked rubber part. It costed about $60. I bought a cracked hose but I wasn't able to replace it because the other side is connected to bottom of the engine and I wasn't able to reach that area. I will try next time when I disassemble more parts. This is what I did after failed smog test.

* replaced air filter
* added seafoam to gas tank
* replaced the rubber part ( the picture is above )

This is the result of new smog test.

15mph 25mph
%CO2 15.4 15.4 ( increased than before )
%O2 0.0 0.0 ( decreased than before )
HC 81/81 39/40 ( decreased than before )
CO 0.14/0.47 0.13/0.30 ( mixed )
NO 271/478 64/484 ( decreased than before )

Probably reducing HC would be my homework in next 2 years. It barely passed. I was just lucky.

Nice job good news on yours. Ill have to look everything over again on mine the Knock sensors did not solve my problem. Its still not passing smog. I have back up cars if i have to non op it for a wile to work on it.

Originally Posted by luckydog

Nice job good news on yours. Ill have to look everything over again on mine the Knock sensors did not solve my problem. Its still not passing smog. I have back up cars if i have to non op it for a wile to work on it.

Knock sensors have no bearing on emissions, LD. They are basically sophisticated microphones tuned to the unique frequencies generated when knocking takes place.

You need to totally tune up or double check every item that can be tuned up to see if its in good shape. Hopefully it will be something as simple as that.

Good read on high HC for your next smog test:
http://www.socale30.com/theforum/vie...38e4b456af86fb

Originally Posted by paperplane94

Good read on high HC for your next smog test:
http://www.socale30.com/theforum/vie...38e4b456af86fb

That is a good write up on causes of Smog. With mine ,I think the valves and pistons may be burnt or worn,because my oil gets polluted quickly with fuel. Original injectors ,may have a leaky one.? it is a salvage yard engine that was stripped sitting in a parted out e34 it was not a pretty sight. It was a hit or miss on longivity running it about 1.5 years for $500. The car runs fine just not buring all the gas. Ill try some things in these links.

Although I passed smog test, I just want to keep maintaing the car well. Today I replaced spark plugs. I don't think the previous owner replaced spark plugs before. The odometer is 150K so plugs are worn out much. One surprise was that two spark plugs holes are full of engine oil. I heard about this and it supposes to be okay but curious why only two of them have deep oil in it. In the attached image, you can get some idea. My next project would replacing a fuel filter.

You need to replace your valve cover gaskets .
There are o-rings per spark plug hole that comes with the valve cover gasket kit and those 2 are more worn than the rest .. easy job Noel
Sent from my Desire HD using Bimmer App

Originally Posted by jhkim

Although I passed smog test, I just want to keep maintaing the car well. Today I replaced spark plugs. I don't think the previous owner replaced spark plugs before. The odometer is 150K so plugs are worn out much. One surprise was that two spark plugs holes are full of engine oil. I heard about this and it supposes to be okay but curious why only two of them have deep oil in it. In the attached image, you can get some idea. My next project would replacing a fuel filter.

The oil in the plug wells is from a old/worn/failed valve cover gasket. It's not a big deal to replace. Theare are several DIY's on the net (and IIRC, Joe - aka Monsignor did a write up here recently).

And the plug in that picture actually looks pretty good to me.

Originally Posted by supertech777

You need to replace your valve cover gaskets .
There are o-rings per spark plug hole that comes with the valve cover gasket kit and those 2 are more worn than the rest .. easy job Noel
Sent from my Desire HD using Bimmer App

Dang Noel, you beat me to it

Originally Posted by BMR_LVR

Dang Noel, you beat me to it

LOL 1 out of a million isn't to bad Steve

Sent from my Desire HD using Bimmer App

Thanks for introducing another project. I will do that next time. When you said the plug looks good, does it mean "well worn out" or "still usable plug" ? I don't know how the original shape looks like so I can't guess if this is worn out enough or not. When I replace mini cooper, the middle rod was worn out but this one still has a solid rod. Also I didn't feel difference after replacing plugs. I wonder if the previous owner replaced plugs before.

Originally Posted by jhkim

Thanks for introducing another project. I will do that next time. When you said the plug looks good, does it mean "well worn out" or "still usable plug" ? I don't know how the original shape looks like so I can't guess if this is worn out enough or not. When I replace mini cooper, the middle rod was worn out but this one still has a solid rod. Also I didn't feel difference after replacing plugs. I wonder if the previous owner replaced plugs before.

It looks well used, but in very good shape. I would not expect you to notice a difference in power uniess the old ones were just burnt away. I'm embarrased to say, but I had a set in my E36 with 140K+ miles and they still performed well. They didn't look nearly as good as yours does above and I didn't notice an appreciable difference in power with the new ones. It is a good thing that you replaced the plugs. Document it for your records. One less tune up element needed

Thanks for the tip. Actually this board is a kind of my records for the car. I will keep updating changes and see what would be the result of next smog test. Suddenly I am waiting for next notice of smog check from DMV.

ummm ... my m20 engine doesnt have this o2 sensor anywhere ... don't all models have o2 sensors ?
and can someone please tell me whats that hose in the 2nd picture in jhkim's post ? my intake boot has this small extension at the bottom of it , but its closed ..filled with rubber ... no hoses connected to the bottom of the boot.... just connected to the AFM from one side , and to the throttle body from the other side ... with the icv ( L-shaped ) connected on the side of the boot

Thread jumper city!!

Originally Posted by David Arabiat

ummm ... my m20 engine doesnt have this o2 sensor anywhere ... don't all models have o2 sensors ?
and can someone please tell me whats that hose in the 2nd picture in jhkim's post ? my intake boot has this small extension at the bottom of it , but its closed ..filled with rubber ... no hoses connected to the bottom of the boot.... just connected to the AFM from one side , and to the throttle body from the other side ... with the icv ( L-shaped ) connected on the side of the boot

Only US models have an O2 sensor, your problem lies elsewhere. Perhaps a vacuum leak.

Also, make a new thread if you want to post again.

Originally Posted by paperplane94

Only US models have an O2 sensor, your problem lies elsewhere. Perhaps a vacuum leak.

Also, make a new thread if you want to post again.

sorry...wasnt quite sure whether it was worth opening a new thread for just one question ...
i guess it was