M635CSI ECU (055) help needed!

[masterdog]

Hi everyone,

I'm trying to fix the a/f mixture problems in my rebuilt m88.
I've added o2 sensor for diagnostic purposes and it shows the mixture leaning out with throttle input, no matter what I do with the AFM (which I've checked thoroughly BTW).

There's fuel pressure, spark, no vacuum leaks.
ECU harness was checked.
All sensors are new.
CSI and ICV are ok.

Although ecudoctors.com checked ECU and said it's ok, I have my doubts.
One of the reasons - I've tried to convert to Miller MAF and could not get it to work. After countless hours of work engine would either stall or was unmanageable.

I've thoroughly inspected the ECU and refilled some solders, replaced capacitors too.
ECU has been messed with before (some components removed - I've circled some on the photo), but I can not tell whether it was done at the factory or later in it's life.
I have searched the web, but could not find any photos of the PCBs of the 055 ECU.

I was wondering if anybody on the board has ever taken photos of the insides and could post them here - this way I could at least visually compare the differences.

Any help is appreciated!

[DesktopDave]

Never took an M635 unit apart, but I'll post a few pics of a scrap 011 unit (Euro M30B35 "dirty M30"). They're both Motronic 1.0 Basic versions, I think. There are a lot of small differences between these two, doesn't look like many parts could interchange.
20141126_155610_zpstwaqwgta.JPG

20141125_194042_zpsgto6cl7a.JPG

[masterdog]

I appreciate that!
I've seen several photos of different ECUs from that era, but never a 055...

[GazM3]

How much leaner is it?

Perhaps you could try a different apporoch. If it's blanket lean well could be fuel related. Perhaps an adjustable fuel pressure regulator can give you a little more fuel getting the mixtures richer.

What at are you doing with the air meter to get it richer. Adjusting the spring tensions, or just the hex as prodominatly this does fuel mixtures at idle and low throttle.

Maybe its worth considering a standalone ecu. Much more versatile than the 055 and u could switch to no Maf, sequential injection, and closed loop fuel control with wideband sensor. This will pickup power and economy as well which is a nice little bonus.

[masterdog]

Basically no matter how rich it is at idle it leans out to the very minimum at throttle.
As if there's something with the fuel map.
Another thing I wanted to try is to stick another chip in it, Dinan or something, in case the problem is with the actual chip, not ECU. Although this will not explain why Miller MAF did not work....

On AFM I have adjusted spring, arm and bypass to compensate.

I'm saving standalone option as a last resort...

[rlkrlk]

How's it run? How do the plugs look?

A misfire will show lean AFR's.

Good luck,

Ray

[masterdog]

It does run ok-ish, it doesn't misfire, but sudden throttle input makes it hesitate or backfire through intake.
Plugs look a bit hot, nothing too bad, but it idles on the rich side, so maybe that contributes to overall healthy look.

And thank you! )

[DesktopDave]

MarkD had written a bit about those early DMEs. I'd personally contact him for a chip tune, he's an expert in the field.

I also found some other geeky goodness about that RCA 1802 chip here. The 055 is an ML3.1 series (Motronic 1.0 Motorsport, NOT a Motronic 3.1!). It matches the 079 unit from the early S38 (according to this page). Similar ML 3.3 are listed here & here.

Check out the Porsche 944 unit here if you get a chance...looks just like yours, but with a few transistors mounted where you have empty space...

[rlkrlk]

Send me your ECU and AFM and I'll install them on my pretty-decently-running-at-present car ;-)

Good luck,

Ray

[GazM3]

An adjustable FPR with a gauge is probably much cheaper than the standalone. You can make wholesale changes then fiddle with the spring on the air meter and adjust the rich idle. Also u can check whether the fuel pump/s are working to their capacity.

If u don't have one install a wideband with airbfuel gauge. I had an issue when replacing an air meter and injectors it was pretty rich. I used a cheap silicone chip fuel adjuster which intercepts the air meter signal and u can correct the fuel at 128 seperate load points in real time. Nowhere near as good as a standalone but I got it running real nice. As the m635 is off the road for a while I borrowed the fuel interceptor for the 540i and i got it running real sweet too.

Hope this helps.

[masterdog]

MarkD had written a bit about those early DMEs. I'd personally contact him for a chip tune, he's an expert in the field.

I also found some other geeky goodness about that RCA 1802 chip here. The 055 is an ML3.1 series (Motronic 1.0 Motorsport, NOT a Motronic 3.1!). It matches the 079 unit from the early S38 (according to this page). Similar ML 3.3 are listed here & here.

Check out the Porsche 944 unit here if you get a chance...looks just like yours, but with a few transistors mounted where you have empty space...

I looked into 079 ECUs. They ARE similar, but additionally require O2 sensor, barometric pressure sensor and purge valve.

The Porsche ECU looks suspiciously similar to mine, it also has the components missing from my ECU that someone removed (those transistors operate ICV btw, not needed on m88).
That's another reason I NEED to see an original unmolested 055 to figure out what I have.
My guess - PO replaced bad ECU with the next best thing - hatched Porsche unit...

Send me your ECU and AFM and I'll install them on my pretty-decently-running-at-present car ;-)

Good luck,

Ray

I appreciate that Ray!
You wouldn't have a photo of your ECU by any chance? )

[rlkrlk]

I looked into 079 ECUs. They ARE similar, but additionally require O2 sensor, barometric pressure sensor and purge valve.

The Porsche ECU looks suspiciously similar to mine, it also has the components missing from my ECU that someone removed.
That's another reason I NEED to see an original unmolested 055 to figure out what I have.
My guess - PO replaced bad ECU with the next best thing - hatched Porsche unit...




I appreciate that Ray!
You wouldn't have a photo of your ECU by any chance? )

What? You wanna verify I have one before sending yours?

I should have a chance to pull it this weekend if it will help. I don't think I even opened this one -- in the 10+ years I've owned this E24.

Cheers,

Ray

[masterdog]

What? You wanna verify I have one before sending yours?

Right now I'm not even sure I have an actual 055 ECU, it may have been replaced with something to make the car work.
If this in fact what happened, I better start shopping for another ECU...

[rlkrlk]

Here's an interesting thread...

http://bigcoupe.com/phpBB2/viewtopic...&highlight=055

The last comment here may also be interesting...

http://bigcoupe.com/phpBB2/viewtopic...35+ecu#p187840

Cheers,

Ray

[masterdog]

Here's an interesting thread...

http://bigcoupe.com/phpBB2/viewtopic...&highlight=055

The last comment here may also be interesting...

http://bigcoupe.com/phpBB2/viewtopic...35+ecu#p187840

Cheers,

Ray

Thank you Ray!
I've seen both threads, there's a good write up on AFMs here: http://www.iprimus.ca/~trauttf/temp/AFM/
It mentions differences between earlier and later units.

Also, people keep talking about ICV control in 055, but m88 (at least mine) has Air Slide Valve that is much simpler that ICV - there's a some sort of spring that receives 12v, heats up and closes the bypass slide AFAIK.

So whoever removed the circuit components that control ICV in my ECU, did know what he was doing.

[masterdog]

Ok, if not the photo, a diagram of the ECU circuitry would help tremendously.
I've looked online, but couldn't find anything...

[rlkrlk]

Yeah, no ICV on mine.

I just pulled the plenum to replace the coolant hoses a month ago when the original water pump started peeing.

Cheers,

Ray

- - - Updated - - -

And I'll try to pull the ecu by Monday, if not sooner!

[masterdog]

Yeah, no ICV on mine.

I just pulled the plenum to replace the coolant hoses a month ago when the original water pump started peeing.

Cheers,

Ray

- - - Updated - - -

And I'll try to pull the ecu by Monday, if not sooner!

Thank you Ray! I really appreciate it!

BTW keep an eye on those plastic coolant tees, especially the one under the intake, near the starter.
PO of my car had one replaced due to failure, I myself simply put a brass one of similar size that I got from Home Depot (you can see it on the second photo).
I did the same with the plastic tees near AFM - replaced with brass, just painted those black.

The Air Slide Valve is also visible on those photos. I understand that the early units were not electrical at all, they would operate by heating up together with the engine, that's why they are all bolted directly to it.

[rlkrlk]

Hmm. I should have pulled the air slide valve and cleaned it. I don't have much of a high idle. Never did, as I recall.

I cracked the tee near the AFM while replacing that line about 2 weeks before the water pump went. The one under the plenum looked good. Though of course you can't tell with plastic, generally.

And no, don't ask me about my timing chain guides. ;-)

Cheers,

Ray

- - - Updated - - -

P.S. I took a pic like that also.

and ran carb cleaner thru the TBs.

The motor ran pretty well with no AFM and plenum. Considering.

[masterdog]

I used 2 brass tees actually to make for one original. Couldn't trust plastic much there...

Just as with m52 engines - people had so many problems with plastic thermostat housings and belt pulleys, many ended up upgrading to aluminum ones.
I know using plastic is cost (and a bit weight) saving, but I'd rather have an extra pound of weight in the car than become stranded somewhere or damage the engine...

BTW is your water pump original? Has it been replaced?
Mine has. With the wrong one installed.
It LOOKED the same, just slightly different impeller design.
I guess PO couldn't find the original one, so he installed the one for m30 engine, that produced about 30% less pressure...
And it took me a while to figure out why is my water circulation so bad...

IMG_4048.JPG

[rlkrlk]

My water pump was date coded 9/84 I believe. The car was built in October IIRC.

Yeah, plastics, ick.

I have an aluminum radiator from the group buy on S38/M88 Yahoo list a couple years ago.

Ok, pay attention, 6 pics to follow.

[rlkrlk]

Looks like no one was into my ECU before, I think...

Lambda box for good measure!IMG_20170702_171428039.jpgIMG_20170702_171417696.jpgIMG_20170702_171408036 (1).jpgIMG_20170702_170648613.jpgIMG_20170702_170503809.jpg[ATTACH=CONFIG]

[masterdog]

Thank you very much Ray!!!

I've looked at those closely and there ARE some differences (I've circled the parts where components are missing or different).
I haven't checked resistor values yet.

I was kinda hoping to simply add/remove missing components on my PCBs and see what happens, but now I see that chips are different part numbers, as well as PCBs...

It is also obvious now that my ECU was in fact something else in the past and most likely belonged on Porsche, but was simply converted by someone into 055 look-alike by removing those ICV transistors and couple of other components....

055b1.jpg

[rlkrlk]

Hmm, well, good luck with it!

I meant to mention that the internet leads me to believe that all big 6 (of the era) water pumps are currently the same replacement part.

Offer still stands if you want me to use my car as the guinea pig with your ECU!

Cheers,

Ray

[masterdog]

Actually, your PCBs (the actual boards, not the components) look exactly like this one from Porsche 944

Attachment 603952