Swapped from 525 DME to 173, now no start?

[quikveedb2]

I realize this is more of a general technical question but hopefully I can get a quick confirmation of my thoughts here in general discussion. Car is a '87 325is, up until now running fine with a 525 DME, almost completely stock, with the exception of a Magnaflow catalytic converter.

I recently purchased a used 173 DME with MarkD chip, and some rebuild 19.5# Mustang injectors from 2 members here. After installing said parts yesterday the car would not start with the chipped 173 DME, but swapping back to the 525 it starts and runs.

Here are my questions;

1. Do both DME's run motronic 1.3?

2. If "no" to question 1, I should still be able to swap from a 1.1 motronic DME to a 1.3 on this vehicle with no other additional parts, correct?

3. Am I accurate in speculating that the 173 DME may be faulty, and should be swapped for a known good unit, or should I look elsewhere first?

Any input would be appreciated, in the mean time I'm going to keep doing research myself.

[e30sh]

1.1 / 1.3 153 / 173 / 380 / 525 etc all plug in and run on an i harness.

Have you tried the Mark D chip in the 525?

[quikveedb2]

Yes. The chip in the 525 seems to be soldiered in place, I didn't want to damage my working DME to try to fix what may be a broken one.

[djjerme]

The 525 shouldn't be soldered in place, the 153 is usually the one that is. I have a stack of them and would have to look again, but I had a 153 for a long time that if I recall I left stock as a control one. The 525 was a later version I thought that came in the iX's specifically.

[quikveedb2]

Interesting. Definitely soldered, and the case is labeled 525.

[TC Baur MD]

525 Chip

I recently replaced the chip in my 525 ecu with a Sssquid one. The ecu was in my 1993 e30 conv. It's my understanding that the 525 ecu was made after the 173 ecu. No problems yet.
Hard to believe yours was soldered in.

[DesertBMW]

173 DME is bad for sure or chip is bad

[nando]

there's little (if any) physical difference between a 525 and 173. Certainly, it didn't come with a soldered chip.

FYI, the 5XX Motronics were for California emissions cars, it's not so much an 'early vs late' thing. Not sure of the exact differences but likely just minor tuning changes.

[KIRIEIW]

there's little (if any) physical difference between a 525 and 173. Certainly, it didn't come with a soldered chip.

FYI, the 5XX Motronics were for California emissions cars, it's not so much an 'early vs late' thing. Not sure of the exact differences but likely just minor tuning changes.

Damn that's kinda interesting, never heard of that.

[TobyB]

there's little (if any) physical difference between a 525 and 173. Certainly, it didn't come with a soldered chip.

FYI, the 5XX Motronics were for California emissions cars, it's not so much an 'early vs late' thing. Not sure of the exact differences but likely just minor tuning changes.

The 525 has a top speed limiter at 128 mph.

Found it when I went from 50 to 45 series tires on the Pro3 car...

t

[nando]

ah, yes it does - I remember that now. Even with a chip, my car still had it - probably because whoever tuned my 'bavauto' chip didn't know how to disable it.

[TobyB]

I just unhooked the vss from the ecu- nothing bad seemed to happen after that.

Hmmm.... maybe that's why that car's so slow, now... ;)

t

[ELVA164]

Added a wrinkle to the brain today!


Fun fact: the 153 is an objectively better tune than the 1.3 stuff. Better power, better economy. Only downside is harsher on/off throttle. Sssquid confirmed this after my butt dyno got curious.