Running issues with the M50B25

[Eddy]

Guys,need some expertiese help!
My baby is sick,and she needs some zone medicine.I have a M50 B25 with Vanos in my E30,and she doesnt work well under 4000rpm(kind of sounds like she`s running on 5 clyndres,but after unpluging the coils one by one I found out that all 6 are running..),and just before the rev limiter she wont go,and starts to loose some steem(like hiting the brake pedal suddenly..).
Now this loss of power before the limiter can be temporarily solved by reseting the DME by unpluging the earth for a few minutes,but after some lovley limiter sounds,she looses it again.....dont know what can that be...
I changed the air mass senzor(cost me a lot!)and the lambda senzor,but it`s not improved a bit...

The engine it self has 280.000km on the clock,but was well maintained by previous owner...

help?

[Eddy]

no one?

[andyborris]

Is the Vanos thing working?

Andy

[Ant]

check the cam and crank posistion sensors dude, if there is any chafing of the wires the signal will be lost @ high rpm due to vibration.

330 ohms accross the pins iirc, PM brianmooooore for any clarification.

[Eddy]

Is the Vanos thing working?

Andy

yes,the valve is new,and the car really sets off above 4k rpm....

check the cam and crank posistion sensors dude, if there is any chafing of the wires the signal will be lost @ high rpm due to vibration.

330 ohms accross the pins iirc, PM brianmooooore for any clarification.

Will do tomorrow,hope it works....

[Brianmoooore]

Have you got the ECU fault light wired up on this car?

[Eddy]

No...this car is ment to be a serious drift chariot,so the most nececery things are wired up,the rest is not..+ witch wire is for the ECU fault

[Brianmoooore]

Grey wire from pin 8 of the ECU (on mine, at least) to pin 8 of the E34 loom engine plug. Connect to a 12v lamp, with the other side of the lamp going to 12V ignition live.
Most cars are designed to go into a "limp" mode and lose serious amounts of performance when this MIL comes on.
I have not been able to find any information on what is supposed to happen with the M50 engine, although on the occasions the light has come on on mine, I can't say I've noticed any difference.

[Eddy]

Update: ECU fault light wired,it comes on,I reset the Ecu,and the car works normal for a while,then its all the same again...all the sensors seem to be working fine,the crank and the cam senders have been chandged for new items....this has to be a ECU trouble.....the car is going to my mentor on monday,will post what he finds wrong,so that someone with similar issues knows what to do..

[Brianmoooore]

Unlikely to be the ECU. It's just doing what it's designed to do.
One of its inputs from a sensor isn't to its liking and it's getting upset about it.
This might be one of the few cases where a code reader is usefull.

[Eddy]

Unlikely to be the ECU. It's just doing what it's designed to do.
One of its inputs from a sensor isn't to its liking and it's getting upset about it.
This might be one of the few cases where a code reader is usefull.

Hmm...my mentor has one,so I hope he finds the bloody glitch in the car...
The only thing that troubles me so far is,that the car doesn`t do this stuff all the time,she has her moments of glory when she pulls better than the E36 M3(tested yesterday ) but then,its back to the neck-braking stopping at full bore....and pore running below 4000rpm...

It also makes back fire noise sometimes(in the intake pipe...)...any sudgestions what this is Brian?

[Brianmoooore]

Don't have enough experience of M50s to make off the cuff diagnoses, but I doubt if it's anything too serious.
Only problem I had with mine was trying to run it with no charcoal canister valve solenoid.
After about 20 seconds of running the light would come on.

[Eddy]

LOL,dont have that connected,beacuse it was broken when I bought the engine...
U do mean the canister originaly mounted under the intake pipe on the right side of the car? a rubber pipe also goes into the TB (third pipe-the one that is the nearest to the firewall...) from that canister-I just put a screw in it and the idle is ok....before,the car didint start well,and the idle was poor....

but I doubt that it could be this,dont have the possibility to try it either....since I havent got the canister

[DanThe]

Have you still got the valve? If this is left un-plugged the ECU see's it as a fault and the light comes on. Ive replaced mine with a 64 Ohm resistor.

Shouldnt make any difference to running though

[Brianmoooore]

Shouldnt make any difference to running though

Does it or doesn't it? Anyone know for sure?
Can't say I noticed any obvious difference with mine when the light was on, but most cars go into a limp mode when a fault is detected to protect the engine and cat.
Resistor can replace the vacuum valve.

[DanThe]

May have gone into the limp mode, but does it really make that much difference to running? Stopping at full throttle and poor running under 4000rpm? I ran mine about for 2 days in limp mode while I got a lambda sensor to replace my faulty one. It would hardly run at all with the faulty lambda connected, but once unplugged and in limp mode it wasnt too bad, down on power but no kangerooing etc

[jmc330i]

Could a duff 02 sensor be causing the problem? (assuming the car has one fitted)

[Brianmoooore]

Could a duff 02 sensor be causing the problem? (assuming the car has one fitted)

Easy way to find out - pull the plug.
These systems are quite clever, in that they can run with a few missing signals, but a false signal might produce some odd results.
All comes down to what the M50 does when the fault light comes on.
Anyone got an E36 or E34 handbook?
Come to think of it, I have an E36 one!
(Returns after five minute read)
There's no fault light shown on the E36 dash diagrams or mentioned in the text!!

[DanThe]

Could a duff 02 sensor be causing the problem? (assuming the car has one fitted)

I was assuming it had been replaced with new?

I changed the air mass senzor(cost me a lot!)and the lambda senzor,but it`s not improved a bit...

[Eddy]

yes,both lambda(O2) and the air mass meter have been chandged....cost me a f... fortune

[Eddy]

Maybe a little update....the problem is only comming to life,when the fuel tank is almost empty....gonna empty the girl completly,and fill her up to the top,to see if its any better....

[Brianmoooore]

How much of the problem appears exactly when the fault light comes on, and clears when you reset the light by disconnecting the battery?

[Eddy]

The complete lot---the poor running,and the nonability to hit the rev limmiter

[Brianmoooore]

If resetting the ECU clears all the fault symptoms, then your version of the ECU must have some kind of "limp" mode. What, exactly, did your engine and ECU come from?
Wonder if it's something like losing fuel pressure on the empty tank, mixture going a bit weak, and going out of lambda range, or low octane fuel triggering the knock sensors and those going out of range?
Definitely needs a code reader on it.

[DanThe]

Didnt think these had knock sensors? I thought it was just the M52's that did?

[Brianmoooore]

Definitely a couple of knock sensors on my ex E34 '93 M50B25 Tu.

[Eddy]

Donor car was E34 525i,93...
where are the knock sensors located?

[Brianmoooore]

bolted to the block under the inlet manifold.

[Eddy]

Every thing seems to be under the inlet with this engine
Well,I cleaned the fuel tank,and it`s not better...the car is going to the mentor workshop today,will post what he finds wrong

[Eddy]

Brian can U tell me whitch loom diagram(the conversion wires..)did U use with the M50 vanos swap? I need to go throu them again,every sender on this engine is new if it was broken,and it still goes into safe mode
Issues with the poor runing are solved(false air going thrue the fucked up golf servo ) so we figured out that it has to be the wiring.....
The test on the diagnostic plug has resulted in a speed signal malfuntion???? WTF?

[Brianmoooore]

My donor was an E34 '93 525i as well. Had just typed a reply to this when the zone went down!!
First is the E34 pin number, then the function, then the E30 C101 pin number.

1, blue/white, oil level dynamic, 2, green/yellow
2, blue/yellow, oil level static, 10, blue
3, red/white, ABS feed, 20, red/yellow
4, black/blue, aircon
5, black/grey, aircon
6, purple/grey, aircon?
7, black/purple, drive away signal
8, grey, ECU fault light, 12, grey (probably not fitted on UK cars)
9, NC
10, NC
11, brown/yellow, 2nd water temp sensor connection
12, brown/purple, water temp, 4, brown/purple
13, green/purple, fuel pump, 13, green/purple
14, black/white, speed signal to cluster, 14, black/white
15, black/green, unloader relays from starter motor, 15, black/green
16, white yellow, Rx data
17, white/purple, Tx data
18, black/yellow, starter, 18, black/yellow
19, white/green, service lights reset, 11, white/green
20, black, engine speed to cluster, 9, black
21, green, ignition, 7, green
22, green/white, ignition, 6, green/white
23, brown/grey, oil pressure, 5, brown/green
24, white/black, fuel rate to cluster, 8, white/black
25, blue, ignition light, 1, blue.

Note that the E30 C101 colours are engine loom side. Some of the wires from the socket to the body loom are different.

[DanThe]

Definitely a couple of knock sensors on my ex E34 '93 M50B25 Tu.

Just to add, the M50B25 non vanos does not have knock sensors, must have been thinking of this at the time

[Eddy]

Note that the E30 C101 colours are engine loom side. Some of the wires from the socket to the body loom are different.

Thanx , just one more question: aldo the colours maybe different,the pin numbers are exactly the same?

[Brianmoooore]

just one more question: aldo the colours maybe different,the pin numbers are exactly the same?

Yes