Did we ever figure out the "Hot Start Problem"

[gearheadE30]

Wow, I had no idea the hot start issue was such a big deal. Surely the cars didn't do this from the factory, so what has changed in all of your cars to cause bad driveablility on a hot start? I'm still plugged in and I have no issues whatsoever...

[twright]

Gearhead E30:

I wonder if that black/white wire is disconnected somewhere else on your car.  It sure made a difference on mine.

[roundel318]

Their cars had been worked on and whoever reconnected the wire?

[Cobra Jet]

My guess would be that the wire "option" is for:

1) connected wire = Euro M42's (or M42's that are overseas which did not have the catalytic converter)

2) disconnected wire = US M42's (or M42's which are Stateside and MUST have a catalytic converter)

I'm also wondering if the Euro M42 DME is different, or more so, if it operates w/ different parameters and that is why the wire HAS to be connected on the other side of the pond....

I'm sure for those M42's on this side of the pond, with the wire needing to be disconnected, that the DME must operate most efficiently and properly based on that "disconnect" - and if that specific wire is erroneously connected, the DME then has to run in some sort of loop (or is it open loop) mode to keep the car running, maybe not as efficiently, but enough so that it does not stall or leave the driver completely stranded.

I'll have to check this wire on mine too, because I have no idea if it is connected or disconnected... (and how many M42 owners actually know about this wire or have ever even had the black plastic covering off of the main firewall harnesses)....

Just out of pure curiousity, for those that have "fixed" their M42's after disconnecting the wire, did any of you notice poor gas mileage or poor engine efficiency prior to finding the fix?


GREAT FIND - this NEEDS to be made into a STICKY for sure!

[maarten_e21]

Thanks!!!!!!!!!
This really solved my warm start problem to.
Installed this engine in my bmw E21 last year and have had problems ever since. Never would have guest this little connector coused all the problems.

Thanks again!

[keflaman]

My guess would be that the wire "option" is for:

1) connected wire = Euro M42's (or M42's that are overseas which did not have the catalytic converter)

I'm also wondering if the Euro M42 DME is different, or more so, if it operates w/ different parameters and that is why the wire HAS to be connected on the other side of the pond....

I have a Snap-On MT2500 scanner and printed out my ECU (aka DME?) info:

ECU Type:  M1.7
ECU hardware:  0261200175
ECU software:  1267356214
BMW hardware:  1727900
BMW software:  001
Product:  949
SID:  0005

My vehicle is a non-cat version and when the receptacle is disconnected the idle goes to crap. When I set the scanner up for the "cat version" and look at the engine data, reference voltage for the O2 sensor is present.

It appears to me the ECU is set up for both cat and non-cat applications and the connector is sort of a "switch" if you will. EDIT: The eprom is actually the "switch" so to speak. US Spec #1.267.356.378; Euro-spec #1.267.356.214

   -If connected the DME looks for an input signal from the Idle Speed CO Pontentiometer, but it must have the Euro-spec eprom #214.

   -If disconnected the DME looks for input signal from the Oxygen Sensor, but that is for US spec eprom #378.

The DME (aka ECU) part number on the case is the same for both US and Euro markets (0261200175).

Wish I could find something in the wiring manual, but there's nothing that jumps out at me and I'm not all that good with schematics anyway:o

[Jak318]

Yes! It worked for me too! TYVM!!!!

[Cobra Jet]

I have a Snap-On MT2500 scanner and printed out my ECU (aka DME?) info:

ECU Type:  M1.7
ECU hardware:  0261200175
ECU software:  1267356214
BMW hardware:  1727900
BMW software:  001
Product:  949
SID:  0005

My vehicle is a non-cat version and when the receptacle is disconnected the idle goes to crap. When I set the scanner up for the "cat version" and look at the engine data, reference voltage for the O2 sensor is present.

It appears to me the ECU is set up for both cat and non-cat applications and the connector is sort of a "switch" if you will.

   -If connected the DME looks for an input signal from the Idle Speed CO Pontentiometer.

   -If disconnected the DME looks for input signal from the Oxygen Sensor.

Wish I could find something in the wiring manual, but there's nothing that jumps out at me and I'm not all that good with schematics anyway:o

~~~

Interesting info!


When you pull your DME out, can you tell us what the numbers are on all or any exterior labels you see?

On an M42 DME here in the US, the Motronic label on it usually has this part number on it: 0 261 200 175.  These DME's are commonly referred to and known as the "175" in the used M42 market or online forums - so when someone is in need of a replacement DME for a US M42, the DME is a "175".  

I'm just curious if your DME is different from a US spec vehicle that has the catalytic system over a Euro which does not.

For an example, here is a good reference of a 91 M42 US spec DME (thanks to M42 Member rallyegolf for posting the pics in his classified ad on here):
http://www.m42club.com/forums/showthread.php?t=7884

[colin86325]

The factory repair manual mentions something about "catalytic converter protection" and how the mixture is enriched slightly to prevent overheating the element.

[ClubSport]

Wow, does the E36 M42 have a Run Like Crap wire?

[keflaman]

~~~

Interesting info!


When you pull your DME out, can you tell us what the numbers are on all or any exterior labels you see?

On an M42 DME here in the US, the Motronic label on it usually has this part number on it: 0 261 200 175.  These DME's are commonly referred to and known as the "175" in the used M42 market or online forums - so when someone is in need of a replacement DME for a US M42, the DME is a "175".  

I'm just curious if your DME is different from a US spec vehicle that has the catalytic system over a Euro which does not.

For an example, here is a good reference of a 91 M42 US spec DME (thanks to M42 Member rallyegolf for posting the pics in his classified ad on here):
http://www.m42club.com/forums/showthread.php?t=7884

Same number on mine as in rallyegolf's pic: 0 261 200 175. The number of the installed chip is 1267356214.

[Meister]

I finally got around to doing this the other day.  I can't believe that it was something so smiple to fix. thanks sports racer, you the man

[e30nub]

sticky this now

[odbod]

Wish I could find something in the wiring manual, but there's nothing that jumps out at me and I'm not all that good with schematics anyway:o

In terms of wiring diagrams see here, using the grid reference look at E6...

The wire comes from the air flow meter to an input on the ECU called LLCO ( maybe Light Load CO2 but thats a complete guess). and shows as "not connected w/catalytic convertor"

http://www.autolib.diakom.ru/CAR/BMW/1991/318%20Series/WIRING%20DIAGRAMS/fig02.pdf

There are wiring diagrams for nearly everything here
http://www.autolib.diakom.ru/CAR/BMW/1991/318%20Series/WIRING%20DIAGRAMS/

I'm retro fitting an o2 sensor to my car (euro non cat) to use with the LPG kit I am installing, once it's in I'll hook it up and see if I get the same problems, euro ECU's are supposed not to work with the O2 sensor hooked up as they need different software, but it may be all to do with this connection.

[keflaman]

In terms of wiring diagrams see here, using the grid reference look at E6...

The wire comes from the air flow meter to an input on the ECU called LLCO ( maybe Light Load CO2 but thats a complete guess). and shows as "not connected w/catalytic convertor"

http://www.autolib.diakom.ru/CAR/BMW/1991/318%20Series/WIRING%20DIAGRAMS/fig02.pdf

There are wiring diagrams for nearly everything here
http://www.autolib.diakom.ru/CAR/BMW/1991/318%20Series/WIRING%20DIAGRAMS/

I'm retro fitting an o2 sensor to my car (euro non cat) to use with the LPG kit I am installing, once it's in I'll hook it up and see if I get the same problems, euro ECU's are supposed not to work with the O2 sensor hooked up as they need different software, but it may be all to do with this connection.

That's why I love these forums! I ran back through the other wiring manual (http://www.theguestroom.net/m42/e30_91_modified_re.pdf) and see it on page 1360-4 as well.

Thanks for the info and I'll be waiting to see what you come up with when the conversion is complete.