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Non-Essential Emission Sensor?

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songzunhuang
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Non-Essential Emission Sensor?

Post by songzunhuang » Wed Mar 18, 2020 5:49 am

So I finally gave up on my rough idle and took my car to my friendly local independent BMW shop. They checked all the same things I already checked and then added a smoke test, valve adjustment and condition of plugs and ignition parts. Everything was fine they said. Of course they found lots of little things to fix up and I went ahead and let them do the work to the tune of $541. That included new alternator bushings, belts and an oil-change. During this, they mentioned something that I wanted to understand better from the bigger brains on this forum.

The shop owner mentioned that one of his mechanics (very experienced) used to work at a BMW dealer back in 1984 and knew my model year car well. He said that for the USA BMW had to add an additional sensor for emissions reasons. These were added at the USA dealers and often they would disconnect them for customers because the sensor would cause issues as it failed. They decided to bypass my sensor and they believe that the car will run better. So, let me try to explain in pictures and words. The sensor was wired in between the mass air flow sensor and the computer. In my picture below, he has bypassed the connector for this (Emissions by-pass connectors in the left of picture) and plugged the line from the computer directly into the mass air flow sensor (right side of picture).
SensorbyPass.png
Sensor bypass arrangement.
SensorbyPass.png (1.4 MiB) Viewed 952 times
So I'd like to know more. Can anyone fill me in?
Oh and the big question. Does it idle better?
Well, I only just got it back so it's too early to tell. Now with California on "Shelter at Home", I am not sure how much I'll get to drive the car. I'll report back, but interested in what the forum members could tell me. Thanks.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

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Ralph in Socal
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Re: Non-Essential Emission Sensor?

Post by Ralph in Socal » Fri Mar 20, 2020 7:45 pm

I spoke to someone much more knowledgeable about that after I saw it on your car. I think about 2 years ago. He said that some disconnect and bypass that retrofit. He didn’t make any claims about its effectiveness as he didn’t have enough experience with the results. Sorry I can’t be of more help.

Shelter in place is vague in enforcement. At this time even the gathering of more than 10 is providing mostly warnings.

I’m not saying be a nonconformist, just be smart about what you’re doing. Attract attention and you’ll receive it. Go about things quietly and without involving others and you may get a warning but they will not take you away in chrome bracelets

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)

songzunhuang
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Re: Non-Essential Emission Sensor?

Post by songzunhuang » Fri Mar 20, 2020 8:55 pm

Ralph in Socal wrote:
Fri Mar 20, 2020 7:45 pm
I spoke to someone much more knowledgeable about that after I saw it on your car. I think about 2 years ago. He said that some disconnect and bypass that retrofit. He didn’t make any claims about its effectiveness as he didn’t have enough experience with the results. Sorry I can’t be of more help.

Shelter in place is vague in enforcement. At this time even the gathering of more than 10 is providing mostly warnings.

I’m not saying be a nonconformist, just be smart about what you’re doing. Attract attention and you’ll receive it. Go about things quietly and without involving others and you may get a warning but they will not take you away in chrome bracelets

Ralph
In any case, I appreciate the response. I'll dig into this more when time allows. I'm anxious to go try this new setup, but there's no where to go! Last night, all of California is under the "Shelter at Home" order. I fear the economic impact has only just begun.

Stay safe down south Ralph. Maybe this is a good time to tinker on cars even more! That can be done at home.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

baders
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Re: Non-Essential Emission Sensor?

Post by baders » Sat Mar 21, 2020 4:02 am

Song I'm trying to imagine what sort of "sensor" would go in between the MAF and Motronic ? Are you sure its a sensor and not simply a resistor ?
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement

songzunhuang
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Re: Non-Essential Emission Sensor?

Post by songzunhuang » Mon Mar 23, 2020 12:29 am

baders wrote:
Sat Mar 21, 2020 4:02 am
Song I'm trying to imagine what sort of "sensor" would go in between the MAF and Motronic ? Are you sure its a sensor and not simply a resistor ?
I've heard about the resistor, but I am uncertain if this is the case here. I was just repeating the conversation I had with the independent repair shop. At this point in time, I am clueless. That's why I reached out to the community. If I get a chance to look into it more, I'll report back.

The shop owner did tell me that I could remove whatever was added in the bypass. Right now there's a pair of connectors unplugged that are zip tied. This looks very "janky" and I don't like it. I'd rather remove whatever it was connected to. Besides, I can see where a smog inspector may get picky when they see a disconnected plug. Being in California, those smog inspectors can be very particular.
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

baders
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Re: Non-Essential Emission Sensor?

Post by baders » Mon Mar 23, 2020 9:03 am

Yep. Trace them out and see where they go. I can't think of any "sensor" that would need to go between MAF and the computer.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement

songzunhuang
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Re: Non-Essential Emission Sensor?

Post by songzunhuang » Wed Mar 25, 2020 9:51 pm

baders wrote:
Mon Mar 23, 2020 9:03 am
Yep. Trace them out and see where they go. I can't think of any "sensor" that would need to go between MAF and the computer.
I did a bit of tracing during a sunny break in the weather. So those plugs go under the intake manifold and re-emerge by the fusebox. They looked wired into a rectangular relay with a bare aluminum cover. There are lots of green wires and what looks like diodes and a resistor. Maybe this is the resistor I heard so much about?

Here are a few pictures. There is enough there that I couldn't just quickly disconnect everything. I think I'll have to take my time and trace those wires. Perhaps I'll be able to just delete that relay?

The aluminum relay (2nd from left) is where the wire connects into. This is attached to the outside of the fusebox.
Fuseblock.png
Mystery relay is 2nd from left.
Fuseblock.png (1.19 MiB) Viewed 744 times
When pulled off of the fusebox, you can see the wires more accurately. The black wire coming from the center right is what is connected to the MAF sensor. The black plastic cylindrical part in the middle of the picture with the green wire connected to is, has the markings of a diode on it.
Wiring.png
Relay pulled away from Fusebox.
Wiring.png (1.26 MiB) Viewed 744 times
Finally, here's what that aluminum rectangular part looks like when pulled from the mount. It looks like a relay? I'm not sure why else it would need 4 legs.
Relay.png
I think this is a relay?
Relay.png (1.21 MiB) Viewed 744 times
OK, all tips welcome about what the heck this is!
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Song Huang
1984 633CSi
Last 7 of VIN: 6997383

glism
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Re: Non-Essential Emission Sensor?

Post by glism » Sat Apr 04, 2020 6:02 pm

Huh, watching this thread. I have the same odd aluminum relay in the exact same spot. Same car too - 1984 633CSI. I'll have to check mine out to see where the wires lead

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jps635
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Re: Non-Essential Emission Sensor?

Post by jps635 » Sat Apr 04, 2020 7:57 pm

I think that could be a purge valve relay.

Read through this about half way down. https://www.bimmerforums.com/forum/show ... -t-fire-up
'85 635csi JPS (RA2-66)

marc79euro645
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Re: Non-Essential Emission Sensor?

Post by marc79euro645 » Tue Apr 07, 2020 12:35 am

purple green wire is fuel pump. Yes that is a relay.

songzunhuang
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Re: Non-Essential Emission Sensor?

Post by songzunhuang » Tue Apr 07, 2020 3:13 am

jps635 wrote:
Sat Apr 04, 2020 7:57 pm
I think that could be a purge valve relay.

Read through this about half way down. https://www.bimmerforums.com/forum/show ... -t-fire-up
You know, I read the thread and I still can't say I know what it is!

Oh well, I drove to the post office today and the car did well. First real drive since I removed the extra wiring tapped into this relay. So far so good.

BTW - I posted a picture of the wiring harness that I removed. It turns out that it went between the AFM and this mystery relay. I removed the harness and cut 3 wires (2 grounds and something else) going to the relay. I left everything else in place until I know more. Pictures of this harness are in my project post.
-----
Song Huang
1984 633CSi
Last 7 of VIN: 6997383

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