What is this? Ignition coil wire

[tomphot]

I bought my Tii and it came with a bunch of extra parts.  This is one of them, nothing on the car looks like it.  I found a picture of another engine bay with this attached to the cover near the distributor.  What it for?

[jimk]

Diagnostic port passengers side.  It's mounted on the valve cover

Edited February 26, 2020 by jimk

[tomphot]

Thanks, so what does it diagnose, how important is it and do I need it?

[02Les]

58 minutes ago, jimk said:

Diagnostic port passengers side.  It's mounted on the valve cover

 

I don't see it, do you have another picture??

[Conserv]

59 minutes ago, tomphot said:

Thanks, so what does it diagnose, how important is it and do I need it?

Tom, 

 

I believe it is not important in a practical sense. In 1972, the techs at your dealer would hook up this plug and the other plug — next to the fuseholder — to their state-of-the-art diagnostic machine and they could tell you.... uh well, something, about your car. I believe the subject of this thread specifically allowed the tech to test the car’s primary wiring. Those diagnostic machines, however, are now more likely seen on American Pickers than in a BMW dealership!

 

The diagnostic plug’s only substantive contribution today is in maintaining the original appearance of the engine compartment. That may be worth something or nothing to a given ‘02 owner.

 

It has one more use, at least to some of us: the presence of a still-in-place original diagnostic plug suggests to me that the car has probably not been substantially modified, repeatedly taken taken apart, or had its engine swapped. This is highly subjective, but there appears to be a correlation between un-molested cars and surviving diagnostic plugs. So I, personally, view these as tell-tales.

 

Best regards,

 

Steve

 

 

 

Edited February 26, 2020 by Conserv

[Buckeye]

see my first post (page1)

 

[Conserv]

27 minutes ago, Buckeye said:

see my first post (page1)

 

That’s the other diagnostic plug, located adjacent to the fuseholder, the one that has survived on 95% of all ‘02’s. I’d guess that 5% or less of the valve cover diagnostic plugs survive. The two diagnostic plugs served different purposes.

 

Best regards,

 

Steve

 

Edited February 26, 2020 by Conserv

[tomphot]

10 minutes ago, Buckeye said:

see my first post (page1)

 

 This is a different plug than the one you referenced. 
 

[jimk]

29 minutes ago, Conserv said:

next to the fuseholder — to their state-of-the-art diagnostic machine and they could tell you.... uh well, something, about your car. I believe the subject of this thread specifically allowed the tech to test the car’s primary wiring

It has an induction coil around the HT wire from the distr center post to the coil and yes, w/o the BMW test machine, it is rather useless.  Store and maybe someday sum purist will buy it for big bucks!

The photo I posted was scanned from a 1972 Road & Track mag road test.

It has provisions to hold 3 of the spark plug wires.  See the OPs pic.

Edited February 26, 2020 by jimk

[Buckeye]

14 minutes ago, Conserv said:

.The two diagnostic plugs served different purposes.

 

6 minutes ago, tomphot said:

 This is a different plug than the one you referenced. 

 

 Please educate me what is the difference between the one on valve cove vs. one on driver side function.

Farshid

[jimk]

5 minutes ago, Buckeye said:

 

 

 Please educate me what is the difference between the one on valve cove vs. one on driver side function.

Farshid

See sht 12 13 011 in the shop manual replacement of coil.   I think section 1 also has info on the diagnostic machine.  The wiring diagram shows the pickup coil on the coil wire.

[tomphot]

I was looking at a BAT listing and noticed this in an engine bay picture and finally saw something that looks like this part that’s been sitting in my parts bin.  If I hook it back up, is there any down side?  Is there wiring that maybe comprised?

 

Edited February 26, 2020 by tomphot

[jimk]

Check it's coil wire first.  That may be the reason it was removed.  If ok, no downside.

[Conserv]

45 minutes ago, jimk said:

Check it's coil wire first.  That may be the reason it was removed.  If ok, no downside.

+1

 

Tom,

 

Many (most?) of these plugs were simply not re-installed after the spark plug wires were changed: owners and BMW techs didn’t want to re-use that coil wire when they had a box of brand new wires. Not that anything was likely wrong with the coil wire, but there is a general feeling that if you’re replacing the spark plug wires, you might want a new coil wire. This was especially the case where service was not performed by a dealership — and, thus, the factory diagnostic machine was not an incentive to re-install the diagnostic plug and wiring — and after the diagnostic machines became dated and were, thus, less central to diagnostics and tuning.

 

Best regards,

 

Steve

 

Edited February 26, 2020 by Conserv

[tomphot]

I going to find a way to test the coil

wire and then would like to reinstall this.  It appears from the one picture I could find that one of the spark plug wires went through this loop, would this have been #1 Spark plug wire?