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Discussion Starter #1
I have had this problem for ages but it hasen't bothered me very much until now.
The symptom is that when driving at low speed (20 -40 Km/h) and releasing the accelerator is cuts down to zero at once. There is a "thump" in the car and it is as if someone pulled the car backwords. Accelerating gently gives the same result, only the reverse. It takes of with a "kick" and a "thump". This is getting anoying. Besides, I believe that this will wear the transmission parts prematurely.
Should I adjust the intake butterflies to a allow for a small amount of air to enter that way even at idle or what should I do? I think the butterflies close completely now, but I have never touched them so I don't know the proper setting.

Any other ideas?

Cheers! :wroom:
 

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If there is a good "thunk", then check the rear axle beam bushes.


If you mean the engine itself, then this I think is fairly normal. For instance, a little game; Try sitting parked somewhere, in neutral, then press the accelarator to go from idle (850ish rpm) to exactly 1000rpm, the first white line.....


Can`t be done. You add more and more pressure to the mechanical cable, but there are six throttle bodies, one per cylinder, which is normal only on bikes and M-Cars, so the cable doesn`t move. Suddenly you have enough pressure to open all six, and the revs jump to 1100+.

Try it the other way is easier, drop the revs slowly to 1000rpm, this is sometimes do-able.

That is why driving the M5 smoothly at low speed around town or in a traffic jam is a talent. The mechanical nature of the throttle system does cause those clunks and jerks when coming off and on the throttle lightly at low speed.

Sometimes I get a "harmonic", especially at very low speed in first, for example in a traffic jam at walking pace, where the car "bounces" forward and back as the play in the gearbox and transmission argues with the car trying to be on and off the idle at 900-1000rpm.

Then again, my car just might be knackered!!! LOL :)




Ivan.
 

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Discussion Starter #3
OK. You just described my car and the driving experience in slow traffic :wroom: :)
I understand that I need to improve my slow driving talent :flag:

Mvh /Ian
 

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I think I would agree with you as this is what I have just noticed buying my LE. There is gearbox play, mine has dual mass/gearbox ratlles on idle and also the throttle is a pain to mudulate smoothly (my previous E39M5 was drive by wire!)

I also notice slightly uneven power at 2-3k - when cruising on the motorway with light throttle and 80 say, you can just feel a little 'tugging' as the engine runs slightly lumpy.

Bit more power on some strokes I guess?

I am putting this all to the 'analogue' nature of this fat 3.8 six.

Cheers
 

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Don´t you just love it!!

I get the same gearbox, throttle position conflicts, especially when the engine is still cold. I can also feel those slight tugs when cruising at low speed.

It´s the "M" division´s way of reminding you that there´s a racing engine under the hood :wroom:
 

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Ivan's first reply that the rear bushes are worn are probably correct. Considering the age of our cars and the fact that probably none of them have had the labor intensive job of changing rear bushes done. I hope to have mine done soon so that "thunk" goes away for another 10 years.

Hey Ivan! I'm glad to know I'm not the only one that has a "bobble" head when driving slow and not paying attention! LOL!
 

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WylM5 said:
I hope to have mine done soon so that "thunk" goes away for another 10 years.

LOL!
I think it might be something else as mine just had new rear subframe bushes. Driveline play and lumpy engines.

Hoping to trace the clonks on low speed bumps and sleeping policemen...
 

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M5Sime said:
I think it might be something else as mine just had new rear subframe bushes. Driveline play and lumpy engines.

Hoping to trace the clonks on low speed bumps and sleeping policemen...
Odd...
I have always thought that my M5 touring -93 was easy to drive at low speeds and very easy to modulate the throttle.....Maybe my car is faulty? ouich
(well it is now with busted timing cahin tensioner etc....)
My girlfriend trained for the drivers license with it summer AND winter(snow etc) and she always liked driving the M5 better that Golfs etc as it was so easy to drive.... :confused2

:cheers:
Sakke
 

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Sounds like alot of people have this uneven driving drving problem at low speeds.


Low speed cruising lumpiness at a constant speed is so annoying and I have been trying to fix it for ages. Cleaning the crank sensor made a bit of a difference but seems like it needs a better clean. The car should not do this and its is 100% a problem. Feels like an airleak somewhere.

I will find this problem.
 

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Discussion Starter #10
All,

I did have a look under the hood during the weekend. I found that when you gently move the accelerator set-up by hand directly on the engine (engine shout down) you hear a tiny "click". I loctaed it to the fuel opening valve at the very front of fuel line tunning across the top of the engine. It seems to match the throttle position where I get the very abrupt acceration/deacceleration. It is actuated by the axle that runs through the air inlet tubes.
I will contact an M5 specialist and find out how the butterflies shall be set in order to aviod this if possible.
I'll keep you posted.

Cheers.

By the way, I just learnt that I will get a new engine for my E39 M5 since the old engine can't be repaired. Water has entered several cylinders and scrateched. I hope to have the car back in a couple of weeks. I am lucky to have the old E34 since I need a reliable car even though I had to replace the alternator three weeks ago ;)
 

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ilundber said:
All,

I did have a look under the hood during the weekend. I found that when you gently move the accelerator set-up by hand directly on the engine (engine shout down) you hear a tiny "click". I loctaed it to the fuel opening valve at the very front of fuel line tunning across the top of the engine. It seems to match the throttle position where I get the very abrupt acceration/deacceleration. It is actuated by the axle that runs through the air inlet tubes.
I will contact an M5 specialist and find out how the butterflies shall be set in order to aviod this if possible.
I'll keep you posted.

Cheers.

By the way, I just learnt that I will get a new engine for my E39 M5 since the old engine can't be repaired. Water has entered several cylinders and scrateched. I hope to have the car back in a couple of weeks. I am lucky to have the old E34 since I need a reliable car even though I had to replace the alternator three weeks ago ;)
Hi!!
OMG!! :eek:
Hope that it`s going to be warranty reparation...... What was the underlying fault?

Sakke
Sakke
 

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Discussion Starter #12 (Edited)
No warranty. Engine insurance on my normal insurance but since the car has more than 40.000km on the clock I have to pay 25% of the $29.909 it will cost. Less than 40.000 Km and it would have cost me $170.
The probable cause is a blown cylinder gasket or a leaking cylinder head. However, since the insurance company decided to put in a new engine they do not investigate any further. We are discussing with BMW to get a Goodwill guarantee, but it is not very likely that we will. :crying:
 

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I recently had an Inspection 2, and mentioned this problem that we have. The technician couldn't put his finger on the problem but had a 'gut' feeling that the engine was running to rich, and maybe needed the throttles balanced; which would support 'ilundbers' findings.




ilundber said:
All,

I did have a look under the hood during the weekend. I found that when you gently move the accelerator set-up by hand directly on the engine (engine shout down) you hear a tiny "click". I loctaed it to the fuel opening valve at the very front of fuel line tunning across the top of the engine. It seems to match the throttle position where I get the very abrupt acceration/deacceleration. It is actuated by the axle that runs through the air inlet tubes.
I will contact an M5 specialist and find out how the butterflies shall be set in order to aviod this if possible.
I'll keep you posted.

Cheers.

By the way, I just learnt that I will get a new engine for my E39 M5 since the old engine can't be repaired. Water has entered several cylinders and scrateched. I hope to have the car back in a couple of weeks. I am lucky to have the old E34 since I need a reliable car even though I had to replace the alternator three weeks ago ;)
 

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you hear a tiny "click". I loctaed it to the fuel opening valve at the very front of fuel line tunning across the top of the engine.

Are you sure that it is not the throttle position switch you here. This is the point where engine speed is transfered from air idle to mass air sensor. If your clunk is coming from the rear it is possibly the differential hanger. This should also show up when backing.
 

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Discussion Starter #15
You are right. I may be the trottle position switch. The clunk sound is more a result of the "binary" on/off of power when I depress or releases the accelerator. I have asked an M5 mechanic at BMW and he will consult some of his friends who are more used to the E34 than he is. I'll keep you posted.

Cheers.
 

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The S62 is almost $30,000 !!!! CRAP! I thought the S38 was expensive. I hope you didn't miss that 40000km limit by too much as 7500 vs 170 to get warranty work done is a HUGE difference. Hopefully as a repeat owner of BMW M cars they will stand by you and give you a break.
 

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This is a strange problem.

I left the car standing for about week and now the car is smooth at any speed.

This doesnt make any sense at all.

Anyways, Im having a complete inspection 2 carried out which will include valve clearances and getting the the throttle bodies cleaned out and balanced.
The crank sensor + pulley will be cleaned also and any airleaks found will be sorted out.

Hopefully it should run alot smoother then.
 

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Cyrus said:
This is a strange problem.

Im having a complete inspection 2 carried out

Hopefully it should run alot smoother then.
Is this a standard part of the Inspection2? Mine is going to Munich Legends for a full inspection and I am going to ask them about the running in general. I am happy with the lumpy idle and it seems ok in traffic. With 125k under her alloys I am keen to see if some of the 340 bhp is missing.. Its a bit lifeless until 4k and then its some action. Thinking of trying some power boost foam/spray that you apply to the inlet manifold and cleans the crowns/valves/working etc. reviewed by some mags and gave 10bhp on their tests.

Just not sure whether to try on my car! after this amount of time things must be a bit gunked up...
 
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