OS2 connection, Help! - BMW M5 Forum and M6 Forums
E28 M5 Discussion 1984-1988

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post #1 of 12 Old 4th October 2005, 05:10 PM Thread Starter
Keeperomega
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Unhappy OS2 connection, Help!

A bit about this car and owner... Bout six years ago, I somehow ended up visiting Bogota, Colombia, on my way to Madrid, Spain; I liked it, I stayed. I mainly enjoyed the simplicity of Colombian life, the beauty of Colombian women, the low cost of living and the miriad of opportunities I found.

Some uneventfull day about year + 1/2 ago, I was offered a Turbo US spec 1988 ///M5 !!! Of course I did not believe it because BMW never made such a beast. Some three months later, I was told about the same beast; that it was almost 80%disassembled, rusting away somewhere, missing parts and that it was looking for a good home, where someone would understand the mechanics of such a modern beast.

Not convinced of the authenticity of the car, I made the arrangements to go see it for myself. Lo and behold...!!!??? it was a real 1988///M5 with a Turbo, 37.000 miles, in apparent perfect condition... It turns out it´s the only ///M5 in the country! Of course, I bought it knowing that it needed tons and tons of loving care, some hard to find parts in a country where the most common mode of transportation is the Renault 4 and other Korean and Japanese numbers, where the minimum wage is US130 dolars per month (60 hours/week), where you can dine and wine with a lady in the best of places, as elegant as in any European city for about US$40.00, but where you cannot get a proper tune up on a VW beetle for lack of proper info.
A year has now passed and the car has been assembled to the best of my knowledge. It´s not a turbo anymore because BMW never meant it to be in the first place. I have managed to obtain some info on engine specs thru the Net, but not enough.
I have been enjoying this car immensely traveling through the most challenging roads in this country´s geography with some of the most beautiful scenery I have ever seen (I once made the trip from Madrid to New Dehli in a VW Fastback), and the ///M5 has shone for all the things it is capable of doing, excellent performance, handling, although it lacks a bit in the brake department due to all the bias problems it came with, but all in all, I have enjoyed it more than anything else I have owned in my life (Porsches, Minis with Suzuki 1300 twin cam engines, AMG Mercedez, and even one older Ferrari).
My problem is:
When the aftermarket turbo was installed, the connections from the ECU (US spec) to the Oxygen Sensor were made to disappear as if they had never existed... Althoug the car runs fine, It is a nightmare to pass emission control tests (recently implemented), and it darkens the plugs when ran in city traffic resulting in slight missfires until they clean up. I believe that the O2 sensor is critical in this case because we are at 2.600 meters above sea level, and one of the most difficult things to do is to properly "carburate" an engine, even if it comes with a Motronic injection as it is the case.

Can anyone help with a schematic of the US spec ECU??? I have not had much luck through the net. The local BMW dealer has never had anything to do with ///Ms until recent years, and only with the ///M3. As a matter of fact, there are only 5 more ///Ms (E34s) in the country and they are stowed away, never used... something might brake??? because there are no spare parts available, no mechanics, no tools, just amazement at the fine machinery!!! Please someone, help me enjoy.
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post #2 of 12 Old 4th October 2005, 06:06 PM
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Re: OS2 connection, Help!

I believe I have a schematic of the ECU at home. I'll scan it if I can remember where I put it.

On a side note.... Do you still happen to have your Turbo manifold? I would be interested in purchasing it if still in your posession.

Thanks!
Jeff

Jeff R.

///M5
1988 BMW E28
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post #3 of 12 Old 4th October 2005, 06:07 PM
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Re: OS2 connection, Help!

Oh yeah and one more thing....

DIBS!

Jeff R.

///M5
1988 BMW E28
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post #4 of 12 Old 5th October 2005, 03:55 PM Thread Starter
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jeffR116:
Thanks for your reply. I hope you can find that so-hard-to-find schematic. As far as the turbo manifold is concerned, the engine was fitted with a DINAN one-piece Six-into-One with increased angle manifold which I had never or have seen in other BMW 6 engine, but it did, and still does the job. I left that one on because of the difficulty of getting BMW parts down here. I am sure there are better aftermaarket manifolds in the states. You must remember that Colombia does not permit the importation of spare parts or used cars or anything of the sort. When I rebuilt the engine I had to pay the local dealer US$350.00 for the set of cylinder head grade 13 screws. I tried bringing them through customs from the states but were "confiscated." I would have had to pay about $400.00 in customs duties (100%) anyway.
I have now disassembled the car again for a complete restoration job; interior although it is near perfect, paint, because it sat in a shop for five years as a table top, suspension has been completely redone to factory specs, and brakes are still a question; engine, because I did bring the new hydraulic chain tensioner from the states, and when I unscrewed the old one, the threads on the cylinder head came out with it. I am taking this as an opportunity to restore the car to its original glory adding some HPs. I am rebuilding to Euro specs with a bit of improvements and detail work to the valves and etc., which should give me some real 330 HPs. Labor is the only inexpensive thing here and I will take advantage of that.
I will be looking forward to your reply.
Thanks
*****************************************
Quote:
Originally Posted by JeffR116
I believe I have a schematic of the ECU at home. I'll scan it if I can remember where I put it.

On a side note.... Do you still happen to have your Turbo manifold? I would be interested in purchasing it if still in your posession.

Thanks!
Jeff
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post #5 of 12 Old 10th October 2005, 08:34 PM
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Re: OS2 connection, Help!

Sorry to disappoint, but I could not find that ECU diagram.... I looked this last weekend to no avail.

Jeff R.

///M5
1988 BMW E28
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post #6 of 12 Old 11th October 2005, 04:59 PM Thread Starter
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Re: OS2 connection, Help!

Quote:
Originally Posted by JeffR116
Sorry to disappoint, but I could not find that ECU diagram.... I looked this last weekend to no avail.
++++++++++++++++++++++++++++
Thanks anyway. Someday when you are not looking... you´ll find it. Then remember me!!!
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post #7 of 12 Old 12th October 2005, 03:09 PM
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Re: OS2 connection, Help!

Congrats on the car!

Being a tech student i searched AlldataPro and Mitchell OnDemand, unfortunately neither of them have any electrical diagrams beyond the instrument cluster and OBC. How is it that they've defeated the O2 sensor to the ECU?

'88 M5 ( sold )
'03 Subaru WRX ( awd= )

Future plans: Ducati 748s and another M5.
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post #8 of 12 Old 12th October 2005, 07:40 PM Thread Starter
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Thanks! The previous owner, the one who installed the turbo, in an honest effort to provide the engine with the richest mixture possible, messed with the ECU, shorted it. He took it to a real magician to have it fixed. This guy figured correctly that by disconnecting the OS2 sensor the ECU would "think" that the car was under full acceleration, thus giving it the richest mixture possible. But they went one step further... they just did away with the connector pins from the connector terminal itself (there are 7 pins open with no wire, nothing).
So now, the pins, the wires, everything dealing with the OS2 sensor and its intended purpose are nowhere to be seen. The problem of not having the schematic is that if I test any of the open connector pins with any kind of voltage, I might damage the ECU. As I understand it, the sensor will send at least one (1) volt, in Lambda mode, into the ECU. If I send this one volt to the wrong place... well I might have to send to the US for a used unit...
I have restored many classics in the past, but I have a very limited knowledge of electric and electronics and do not trust anyone here... We are about twenty years behind on that kind of technology. People at the local BMW dealer just shrugg their shoulders... everyone else is empirical and they use the trial and error method, which I do not want done with the only US spec ECU in the country.
I will be posting some pictures of the car within the next days. I have now started to take it completely apart for restauration.


Quote:
Originally Posted by schumi
Congrats on the car!

Being a tech student i searched AlldataPro and Mitchell OnDemand, unfortunately neither of them have any electrical diagrams beyond the instrument cluster and OBC. How is it that they've defeated the O2 sensor to the ECU?
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post #9 of 12 Old 27th October 2005, 05:59 PM
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Re: OS2 connection, Help!

I found the Motronic unit wiring diagram

Give me a day or so and I'll post it up here for you.


Jeff R.

///M5
1988 BMW E28
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post #10 of 12 Old 27th October 2005, 06:45 PM Thread Starter
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Smile Re: OS2 connection, Help!

Maximillian thanks a million!!!



Quote:
Originally Posted by JeffR116
I found the Motronic unit wiring diagram

Give me a day or so and I'll post it up here for you.

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