E39 540i - Help! Intermittent "cut-out"

VivP

Member
Good day fellow Fantics.

My E39 540 (1998 non-Vanos) has recently developed an intermittent problem, and I am hoping that a Guru-Fanatic has come across this before and knows the cause & solution.

The symptoms are fairly simple - she'll occasionally "stall" while either stopped at a traffic light, or while creeping slowly in very heavy traffic. At first I thought my clutch-work was dodgy, but then I noticed she'll also do it while in neutral.

A quick swing of the starter, and she is back to life, no further issues.

But then I saw that she would also "stall" - but more like just a cut-out - while cruising on the highway at a hundred and plenty. The stall or cut-out - call it what you will - is only very brief, maybe just a second or less. But is absolute, almost as though you have turned the ignition off and then on again. Because of the momentum and being in gear, she starts again (a second or so later) with no further problem. Until the next time.

During this very brief cut-out / stall period, I noticed that the econo-meter swings all the way to the right (maximum), whereas if you take your foot of the accelerator while cruising, the needle would naturally drop to zero.

A road trip this weekend to EL from PE, this happened 5 times during the 300km-odd trip. When driving in town, say a trip to the shops, I'd see it once or twice. Sometimes not at all. The ride back from EL, it only happened once.

Needless to say, it is quite alarming when this happens mid-way while overtaking and a big truck is heading towards you.

In closing, no work has been done on the car recently, so it's not that. Yes, I did disconnect the bowden cable from the ASC servo-motor to the throttle-body, thinking it might be something dodgy there, but no, that made no difference.

Anybody out there who might have come across this before?

Much thanks.
 

Ralf*

///Member
these are exactly the same symptoms to the "TEE" that my E38-740i was doing

the advice given to me was that it could be
1) Idle control valve
2) Mass airflow sensor

I disconnected the MAF, basically forcing the ECU into a more "basic" programme, and since then all the issues of stalling have been resolved.

financially I don't have the resources to purchases a new MAF at over R6000, and I only drive the 7 series once a week to keep all the systems oilled and battery charged, so for now, that his how it is

according to Peter (alexander) I am doing slow long term damage to the cylinder sleeves, due to overfuelling and washing the sleeves with excess fuel

the consumption is now in the 20l/100km range, where previously it was around 18l/100

You could attempt the same "backyard" trick of disconnecting the MAF, for the interim, whilst you get the codes read, and purchase the correct spares, as I mentioned, I was told that it could either be the ICV or the MAF.....but which one is it ?
 

jcwdrop

Member
MAF is not R 6000. You can get it from VW for less than R 2000. I don't have time to link to the thread right now, but there was a M5 discussion regarding this.
 

VivP

Member
Ralf* said:
the consumption is now in the 20l/100km range, where previously it was around 18l/100

My 350+ km trip from EL to PE, cruising at 120-140 kph, my consumption tallied out out 10.8 L/100km. Not too bad for a big 4.4 L V8 old girl. :tiptoe:


Ralf* said:
the consumption is now in the 20l/100km range, where previously it was around 18l/100

My 350+ km trip from EL to PE, cruising at 120-140 kph, my consumption tallied out out 10.8 L/100km. Not too bad for a big 4.4 L V8 old girl. :tiptoe:


jcwdrop said:
MAF is not R 6000. You can get it from VW for less than R 2000. I don't have time to link to the thread right now, but there was a M5 discussion regarding this.

ummm - why would VW sell a MAF for a E39 BMW 540 ?
 

jcwdrop

Member
VivP said:
Ralf* said:
the consumption is now in the 20l/100km range, where previously it was around 18l/100

My 350+ km trip from EL to PE, cruising at 120-140 kph, my consumption tallied out out 10.8 L/100km. Not too bad for a big 4.4 L V8 old girl. :tiptoe:


Ralf* said:
the consumption is now in the 20l/100km range, where previously it was around 18l/100

My 350+ km trip from EL to PE, cruising at 120-140 kph, my consumption tallied out out 10.8 L/100km. Not too bad for a big 4.4 L V8 old girl. :tiptoe:


jcwdrop said:
MAF is not R 6000. You can get it from VW for less than R 2000. I don't have time to link to the thread right now, but there was a M5 discussion regarding this.

ummm - why would VW sell a MAF for a E39 BMW 540 ?




http://www.bmwfanatics.co.za/showthread.php?tid=68155&page=2
 

Sankekur

///Member
VivP said:
Good day fellow Fantics.

My E39 540 (1998 non-Vanos) has recently developed an intermittent problem, and I am hoping that a Guru-Fanatic has come across this before and knows the cause & solution.

The symptoms are fairly simple - she'll occasionally "stall" while either stopped at a traffic light, or while creeping slowly in very heavy traffic. At first I thought my clutch-work was dodgy, but then I noticed she'll also do it while in neutral.

A quick swing of the starter, and she is back to life, no further issues.

But then I saw that she would also "stall" - but more like just a cut-out - while cruising on the highway at a hundred and plenty. The stall or cut-out - call it what you will - is only very brief, maybe just a second or less. But is absolute, almost as though you have turned the ignition off and then on again. Because of the momentum and being in gear, she starts again (a second or so later) with no further problem. Until the next time.

During this very brief cut-out / stall period, I noticed that the econo-meter swings all the way to the right (maximum), whereas if you take your foot of the accelerator while cruising, the needle would naturally drop to zero.

A road trip this weekend to EL from PE, this happened 5 times during the 300km-odd trip. When driving in town, say a trip to the shops, I'd see it once or twice. Sometimes not at all. The ride back from EL, it only happened once.

Needless to say, it is quite alarming when this happens mid-way while overtaking and a big truck is heading towards you.

In closing, no work has been done on the car recently, so it's not that. Yes, I did disconnect the bowden cable from the ASC servo-motor to the throttle-body, thinking it might be something dodgy there, but no, that made no difference.

Anybody out there who might have come across this before?

Much thanks.

My e34 has in the past had an issue similar to this, but after a good idle control valve clean and fixing a lot of vacuum leaks this issue has been sorted for the most part, though I still recon the ICV is on the dodgy side.
That being said mine only ever cut out just as I came to a stop and never while driving, and that would pretty much rule out the ICV for me as it should be closed while cruising.
I am thinking crank position sensor maybe? Momentary dodgy values from the CPS would cause the motor to stall as the DME cuts fuel and spark the when it doesn't get proper values from the CPS. Though it is of interest to me that it is able to start right after stalling, can't really think of a reason why it would fail so momentarily.
 

Ralf*

///Member
Sankekur said:
VivP said:
Good day fellow Fantics.

My E39 540 (1998 non-Vanos) has recently developed an intermittent problem, and I am hoping that a Guru-Fanatic has come across this before and knows the cause & solution.

The symptoms are fairly simple - she'll occasionally "stall" while either stopped at a traffic light, or while creeping slowly in very heavy traffic. At first I thought my clutch-work was dodgy, but then I noticed she'll also do it while in neutral.

A quick swing of the starter, and she is back to life, no further issues.

But then I saw that she would also "stall" - but more like just a cut-out - while cruising on the highway at a hundred and plenty. The stall or cut-out - call it what you will - is only very brief, maybe just a second or less. But is absolute, almost as though you have turned the ignition off and then on again. Because of the momentum and being in gear, she starts again (a second or so later) with no further problem. Until the next time.

During this very brief cut-out / stall period, I noticed that the econo-meter swings all the way to the right (maximum), whereas if you take your foot of the accelerator while cruising, the needle would naturally drop to zero.

A road trip this weekend to EL from PE, this happened 5 times during the 300km-odd trip. When driving in town, say a trip to the shops, I'd see it once or twice. Sometimes not at all. The ride back from EL, it only happened once.

Needless to say, it is quite alarming when this happens mid-way while overtaking and a big truck is heading towards you.

In closing, no work has been done on the car recently, so it's not that. Yes, I did disconnect the bowden cable from the ASC servo-motor to the throttle-body, thinking it might be something dodgy there, but no, that made no difference.

Anybody out there who might have come across this before?

Much thanks.

My e34 has in the past had an issue similar to this, but after a good idle control valve clean and fixing a lot of vacuum leaks this issue has been sorted for the most part, though I still recon the ICV is on the dodgy side.
That being said mine only ever cut out just as I came to a stop and never while driving, and that would pretty much rule out the ICV for me as it should be closed while cruising.
I am thinking crank position sensor maybe? Momentary dodgy values from the CPS would cause the motor to stall as the DME cuts fuel and spark the when it doesn't get proper values from the CPS. Though it is of interest to me that it is able to start right after stalling, can't really think of a reason why it would fail so momentarily.

Yup, my E38 is closer to yours, it would cut out at the instant moment when I came to a stop, but never whilst at speed
I do however have a slight "hunting" whilst at speed, I can see the RPM gauge fluctuate a mere millimetre and I can see the "econ" gauge also follow the hunting trend, very slight, but I can feel it in the seat of my pants
 

applehero

///Member
My guess would probably be O2 sensors. Get the fault codes read, that may point you to something more specific
 

Clownshoe

Active member
I think that symptom could be related to any number of sensors or relays. I had a similar issue with the e30 325i. It was a faulty relay.

Best bet is to have the codes read.

Does the revs drop to 0 or do they match the in gear engine speed?
 

VivP

Member
Clownshoe said:
I think that symptom could be related to any number of sensors or relays. I had a similar issue with the e30 325i. It was a faulty relay.

Best bet is to have the codes read.

Does the revs drop to 0 or do they match the in gear engine speed?

Revs match geared engine speed.
 

VivP

Member
Firstly, thanks for all the input.

Took The Beast to a reputable local BMW bloke, just around the corner from me. He read the fault codes, ran diagnostics, etc.

As mentioned by applehero, the O2 sensors showed up as faulty - but so too did the MAF, as mentioned by Ralf*. The BM dude suggested that there was nothing wrong with the O2 sensors, and that fault is caused "downstream" by the faulty MAF.

Bought a new MAF from D-E in Port Elizabeth (R2793 inc VAT) - identical Part # - and now The Beast drives like she should again.

Fault codes will be cleared "after driving some", and I will then report back if all is good.

:ty: to both Ralf* & applehero
 

Ratslaaf

///Member
Good call on the MAF and I can only echo what Peter said: Do NOT drive your car without a MAF, especially on short distances. You'll be running rich and will end up with bore wash.

There's many things that exhibit this behavior and diagnostics is pretty much the only way to determine the culprit without wasting money. I had a car with an M54 engine here yesterday with the same symptoms and the cause was the inlet cam shaft sensor. 3 days ago, on another M54, the issue was the crank sensor.

On yet another car last week, it was a dud replacement MAF sensor
 
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