E34 m50 cold (morning) start problem

[karmann]

I have a e34 520i (m50) the car started to have problems last winter
when it started to get cold it became increasingly hard to start in the
mornings and finaly refused (it sounds as if the car doesnt know its cold so it doesnt send fuel)
. after changing coils,plugs unplugging
airflow (maf),oxygen sensor nothing would help, in the morning (would eventualy start after a long time) finaly unplugged the crankshaft position sensor and
it starts after about 2-3 seconds.( I ran the car like this until last week)
I changed the crank position sensor but it still doesnt want to start in the
morning unless I unplug it..(once warmed up I can plug it bak in and
starts and runs beautifuly) I dont know what else to do ´maybe change
the ecu or the relay (anybody have any ideas)

...I took the car to the dealer 3 days ago and theyre stumped as well .
they changed the crank position sensor again,and the camshaft sensor as well, nada....
the computer is only showing the error for those parts...
I think my wallet is about to be raped.!!
(should I just keep driving it with the crank position sensor unplugged...(its been that way for a year now...no solution in site)
what damage does this do (aside from obvious less power, more fuel consumtion )

[stu1]

I suspect by unplugging the crankshaft sensor the ECU is reverting to a limp mode and hence is ignoring a lot of the sensor information. Have you tried the temperature sensor(s)?

[karmann]

no but should they read that at the dealer if its bad .I was thinkin the same thing so I mentioned it to them

[karmann]

I also think it would be more of a sensor thing since it starts right up as soon as I unplug hte sensor and it goes to limp mode.

[stu1]

I'm not sure if it's possible for the sensor to go bad and not show up on diagnostics, but then I wouldn't believe anything a dealer told me :)

Item 13 on the diagram below is the coolant sensor:
http://www.realoem.com/bmw/showparts.do?model=HB52&mospid=47370&btnr=11_1282&hg=11&fg=15

I take it when it's warmed up it's all fine - normal power, no strange noises etc?

[karmann]

do you know if thats the only temperature sensor on the car that works with the computer

[karmann]

yep actualy as long as its not cold outside
i can plug the crank shaft sensor in right away
but when its cold i have to wait for the car 2 warm up or else runs like crap

[karmann]

ok gonna tell them to look into the temp sensors 2morrow..

I will update this as it continues
as long as I can still afford my internet and computer after Im done...:{
thanks a million....

[stu1]

There are two sensors; I believe you can test them by measuring their resistance - the values are given in Bentley (which I don't have access to at the moment).

Failing that I wouldn't think new ones would be too expensive from the stealer.

Good luck :)

[karmann]

oh 1 more thing ...
when its warmed up I can leave everything plugged in and i can restart fine.
when everything is plugged in it starts in less than 1 second ...I guess cuz the comp doesnt have to switch over to limp.

[karmann]

Ok maybe due to the age of the car I should just have them changed if its not too expensive...thanks again

[karmann]

OK quick update here got my car bak from the dealer.they said they ran it through the computer,only error was camshaft sensor so they replaced it ,now the computer is reading noo errors .but still has the same problem...so 360 dollars for nada! the onlly thing the mechanic suggested to me was to find another ecu and see if that helps. I asked him to check the temp sensors ,they said everything checks out ...but it wont start cold unless I unpug the crankshaft position sensor. so nowI have changed ..
Oil cover gasket
engine coils
fuel pump, filter (also air filter)
spark plugs
crankshaft position sensor
camshaft sensor
I think the next thing I will change is the name brand of car!
(maybe if I put a Mercedes logo on the front it' start...hmmmmm jk!)

[karmann]

Does anybody know which parts of the car work only when the car is warming up? or is it just the computer which changes everyhting?

[stu1]

There is an air temperature sensor mounted next to the the throttle body on the inlet manifold. At 20 degrees C this should read between 2.1 and 2.9K ohms.

It would be a good idea to verify this before going any further and/or more expensive (along with the engine coolant temperature sensor (same resistance reading at 20 degrees C) - this is the front one of the two in the cylinder head under the covers).


Stu.

[karmann]

Ok thanks, I will ask my mech to look at it but I think I have to w8 a bit till I have money to open this can of worms again...
gonna have to keep driving it in limp mode for awhile..:(
this is so wierd the car wont even run with everyhting plugged in while its cold.but as soon as its warmed up i can plug evrything bak in and it starts and runs perfect.
I noticed I use probably 20 percent more fuel in limp mode,
I have less hp,and the care is louder...:( (could it just be me )
keep your fingers crossed for me that I make the winter,..and thanks for the help...OZ

[everlast]

Definately the engine coolant temperature sensor would likely be the main problem. My e30 (m20b27) suffered a similar problem.

I don't have a Bentley here with me, but can anyone else chime in: does the m50 have a thermo-time switch also?

In any case, these deviced tell the car when its cold. I would change them before anything else. See if you can borrow the part to put in, they're not hard to change, so it doesn't cost you any more.

[karmann]

So you think I should change it anyways...they said they tested it at the dealer and it's fine...
the thing that gets me is ,,,the car knows its cold cuz it won't run at all cold..
even if i unplug the cps start it up .I cant plug it bak in until its warm..if it ran allitle rough cold than I would suspect more the temp sensor...but there is a difference between cold and warm running...which leads me to believe something that only works to "warm up the car" is probably causing the problem..
so if there is no cold start injector or any other mechanical part that works only during warmup .I suppose the only other culprit could be the DME ..
or maybe something electrical that is not making a good connection until warmed up...
sorry to make this sooo long ...I just don't really have a clue or a dolllar for this .but I appreciate the help...thanks....

oh BTW I just got bak from a 6 hour drive (700 km)
everything went fine ...although now that i got home I noticed the muffler was a bit louder than normal...maybe the cat is allitle hot I dunnow will c 2morrow.....