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jeffbebe

M70 mystery plug

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Anyone know where this should go?

post-16586-0-04181400-1405390915.jpg

Noticed it over the weekend while I've been servicing the car but can't find anything it should plug into. Looks like a sensor plug but not sure where it should go. It's got a reasonably long cable that appears to go into the DME box (though it's hard to trace that end of it). It was lying as pictured but could easily connect to something lower down... I just don't know what and can't see any obvious socket for it. Can anyone enlighten me?

post-16586-0-22916500-1405390920.jpg

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That's what I figured but can't seem to locate the socket for it? Not sure if I'm blind or just being dumb... Or both.

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Page 9 is a negative but am thinking p.19 is a definite possibility. Would make sense with the cable's location and would make sense why I can't see where it's supposed to go... Now to work out how to get at it to have a proper look. Another job to add to the list.

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Surely if it was a sensor, it would be throwing a code?

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Some codes cannot be seen and I haven't scanned it yet.

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Can you pull back the shroud to see the colours of the wires, then cross reference to a wiring diagram?

It looks like a fairly generic- two pin sensor plug, so could cover a whole host of things - temp, pressure, etc.

Might explain your horrendous fuel consumption if it's not connected to something it should be - like temp, thinks its cold so over-fuelling??

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Exactly what I'm thinking, Jon. Looking at that PDF Martin posted on p.19 an obvious culprit (and well hidden) is the temp sensor at the rear of the manifold. You can't see it without removing stuff so could easily have been pulled out and then the PO have not known where to put it.

EDIT: Hmmnnn... No joy with that one. Just can't see anywhere it could come from, will have to check wire colours as Jon suggests and see what that turns up.

Edited by jeffbebe

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May not actually be used for anything. There are always spare plugs on any car. Pretty dirty inside? suggests its never been plugged in?

Could try searching for it here but might take ya a while http://www.bmw-planet.com/

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Im sure one or two of my cars have plugs that are redundant, same thing....go to nothing

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May not actually be used for anything. There are always spare plugs on any car. Pretty dirty inside? suggests its never been plugged in?

Could try searching for it here but might take ya a while http://www.bmw-planet.com/

Im sure one or two of my cars have plugs that are redundant, same thing....go to nothing

You're probably both right but I'm just suspicious when the car is running super rich and there's a sensor-type plug not attached to anything!

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All M70s run rich.

in the DME box there is a temperature sensor that communicates with a fan in the box. Some markets the fan is wired to run all the time so no sensor. That would be my best guess.

If its anything directly critically related to the running of the engine, there will be one exactly the same on the other side of the engine bay. so if there is only one, it wont be anything like inlet air temperature etc etc

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DME temp sensor on the water coolant crossover pipe seems to be a common cause of rich running M70. If this plug is meant to connect to that sensor... Wherever it is, could explain shite fuel consumption. Will investigate further in daylight.

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Cute that you are complaining about lack of room around the V12 in your enourmous engine bay :P

on the earlier type M70 there are three sensors on the back of the head on right hand bank (drivers side on your car, between the head and the firewall), cant remember what they all do, but they are there, and i know one is for the cluster. one is probably DME and the other Fan or something like that.

Im not sure if they are on the later M70/M73 but i can check tomorrow, its pouring with rain here so im not about to go check!!

If you want me to take pictures I will of the 750iL thats here, the 550 Touring has no room, and is the earlier type engine anyways.

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Thanks Andy. I pulled the cabin filter assembly out yesterday to eyeball those 3 coolant sensors and they're all plugged in so I'm still in the dark but thinking more and more it's just a superfluous plug.

Failing DME coolant sensor seems to be a common cause of over-fuelling (according to Google) and is a cheap replacement so might do that... Trouble is, I'm not entirely sure which of the 3 at the back is the DME one!

PS All the space is at the front in the E31!! The frickin' sensors are all at the back!!

Edited by jeffbebe

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How bad is the fuel consumption? I wouldn't expect anything better than 18-22l/100km around town and maybe 12.5 on a trip? Is it worse?

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How bad is the fuel consumption? I wouldn't expect anything better than 18-22l/100km around town and maybe 12.5 on a trip? Is it worse?

Worse.... 14-15L/100 on a trip and 25L+ around town.

BOOOOOOOOOOOOOOOST!

Because that will solve all the problems, Josh! ;)

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well if there is so much fuel getting dumped in there, you might as well compliment it with more air ... BOOOST

  • Like 1

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Worse than a 493hp S55 Kompressor, good effort. Hope it's a sensor or something.

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well if there is so much fuel getting dumped in there, you might as well compliment it with more air ... BOOOST

Good point!

Worse than a 493hp S55 Kompressor, good effort. Hope it's a sensor or something.

Me too... Comms are down though so no point doing anything until I can find out why comms aren't working. BM Workshop said they would basically have to start the clock then unplug every module starting with the easiest, until the find the one that's causing the issue... Bugger! But better sorting that than throwing cash at parts on the off chance they are faulty.

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Worse.... 14-15L/100 on a trip and 25L+ around town.

Because that will solve all the problems, Josh! ;)

Yep thats worse than mine, best i have seen is 10.7L/100km and that was on a run to coromandle with my great grandma in the car.....

usually 12 on the trip too or from Auckland, including passing every oppertunity, and a good bit of fun through the Ohakune National Park Road.

But 25L/100km around town is very achievable. I have had mine in the 30s

well if there is so much fuel getting dumped in there, you might as well compliment it with more air ... BOOOST

hahaha

Edited by _Ethrty-Andy_

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