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e28 eta Motronic woes

 
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Skrape



Joined: 13 Dec 2002
Posts: 98
Location: Denver, CO

PostPosted: Sat Mar 06, 2010 10:32 am    Post subject: e28 eta Motronic woes Reply with quote

I'm helping ressurect an '84 533i that has been "retrofitted" with an Eta motor. The car is otherwise too nice to write off. The current combination does run and is tantalizingly close to being "fine", but not quite. We think the problem is in Motronic land, and are hoping some Motronic-head can spot the prob or make helpful suggestions. I'm not new to searching the forums, BMWs, motronic, or injection troubleshooting, but haven't yet figured this one out.

Here's what we see:

When we put an '021' or '027' ECU from a 325E on the car, it idles pretty well, but revs reluctantly and feels like it's making about 15 horsepower - it can be driven, but is completely gutless. Waiting for the car to warm up and the ECU to recalibrate didn't change the situation noticeably.

When we put the '008' ECU that originally came on the 533i on the car, at first it revs eagerly and has okay power under load, but idles unevenly. As the car warms up (and/or as the ECU recalibrates), it starts to miss badly under load and the idle worsens.

When we replaced the gray 'eta' low-impedance injectors with yellow high impedance (~14 ohm) injectors (research says these are the 533i injectors, we found 'em in the trunk), the situation doesn't change too much with either ECU.

Some factoids:
- We've been through the wiring harness, checking continuity pin-to-pin against the wiring diagrams in the Bently and the BMW Electrical Troubleshooting Manual found online, without finding any opens or shorts.
- All the sensors, injectors, switches, speed sensor, reference sensor etc have been checked and electrically appear to be okay.
- There is no barometric sensor currently, we're at ~6000 feet altitude so we jumpered the lines for it. This did not appear to make much difference, with either ECU.
- The #6 plug wire had a weird inductive pickup on it, that was not plugged into anything. A plugwire set was installed that did not have this. Research tells me that this is the original 533i plug wire configuration, but there is nowhere to plug it into on the current harness, so I think we've got a 528e harness.
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Sat Mar 06, 2010 3:45 pm    Post subject: Reply with quote

How do you know that the eta engine is in good condition? Did you run it in the donor car? How about the ECU from the donor car? Do you have a copy of the E28 Bentley's? Is it helpful here?

Sorry I can't be helpful, but, you are correct: this job needs a real E28 master. I wonder if any are still alive, or remember the arcane details you need?

Might want to post this on an E28 board, like http://bimmer.roadfly.com/bmw/forums/e28/.
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Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.
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Skrape



Joined: 13 Dec 2002
Posts: 98
Location: Denver, CO

PostPosted: Sat Mar 06, 2010 8:01 pm    Post subject: Reply with quote

Well, the engine seems pretty happy in those minutes with the 008 ECU before it gets, well, unhappy - Feels like a tuning issue. (Compression is OK and balanced, no smoke, etc.) The donor 027 ECU is from my own E30, and had no problems. And yes, we do have both E30 and E28 Bentley's, and we so far haven't found an answer there.

As to the other thing, that's why I posted here - seeking that E28 or Motronic blackbelt - or maybe the neophyte that just asks the simple question I've neglected to ask. (Thanks for your questions, BTW!) I'm still trying to figure it out - anybody else got input?
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dale



Joined: 22 Aug 1999
Posts: 3087
Location: Seattle, WA USA

PostPosted: Tue Mar 09, 2010 1:13 pm    Post subject: Reply with quote

Have you read the wiring diagram for your car at this site?
http://www.wedophones.com/BMWManualsLead.htm

Please use the factory correct 027 DME and other factory specified 325e/528e parts, it will minimize the variables in trouble-shooting this issue.
Do you have spare eta parts that are known good and working in another eta? That can be the fastest way to troubleshoot something like this, swap some parts with another known good eta.
Also keep the correct eta injectors installed, putting in high vs low impedance may damage the DME.

Swapping the DME from a totally different motor, I'd just expect random behavior.

Have you tested Voltage output of your AFM? Easiest way is to either pop the black top off of the AFM, or pull back the rubber on the harness connector and measure the output voltage.
Measuring resistance across the sweeper doesn't tell you much.
Measure output voltage and insure it changes smoothly as you manually open the flap.

That extra connector on the plug wires is used on newer Motronic systems, like the Motronic 1.1 and 1.3 used on the 325i.

OK, I see the 008 DME is also Motronic 1.0, but it's tuned to supply fuel for 3.3L of displacement vs 2.8L, and also tuned to use the larger AFM that is in the M30 3.3L motor.
I'd expect it to run very rich.

Code:

533i E28 M30/B32 84 0 261 200 008 Bosch Motronic M1.0 Basic
528e E28 M20/B27 9/84-12/86 0 261 200 027 Bosch Motronic M1.0 Basic

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87 325 5spd eta
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