2002 325i pulls unevenly

Michael K

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#1
Hi Guys,

I'm experiencing a strange problem for (I guess) 5,000 km now. Car is
2002 BMW 325i, 66,000 km on the counter. What's tricky is the
transmission - it's SMG. For those who do not know, it's a manual
gearbox + clutch, both connected to a hydraulic system that controlls
the gear change. So you have only two pedals, like in a regular
automatic, and gear changes are done with paddles at the steering wheel
or through impulses at the gear change knob.

Good - so now to the problem. Whenever I make a gear change the first
two seconds of acceleration are doen in an *uneven* fashion - that is,
during those seconds I experience something like a slight shudder, or
like a slight hesitations. What could that be? Sign of a worn clutch?
The guibo?

What should be noted (mostly my guess): due to the SMG mechanism, gear
changes at high RPMs are done *very* quickly (that's the lovely part of
an SMG, the rest are downsides...) and so for example when you change
at 5000+ you experience real kicks in the seat - my guess is that such
a system stresses the clutch and other transmission components quite
heavily. The car is driven 1/4 of the time with under 4000 changes, the
other 3/4 with over 4000 RPM changes (out of these 3/4, 80% are over
5000).

My hopes of meeting folks with SMG and similar problems (and hopefuly
solved!) are minimal. However, did/does anybody with a regular manual
gearbox experience such acceleration problems? Maybe we can make a
connection...

Something that might be significant: when the car warms up, the problem apparently goes away.

Thanks a lot guys!

P.S. The dealer does not seem to be very qualified at finding this
problem. Recently he stated that headlight covers can't be changed
(mine were badly blurred by high speed driving - dust and small stones
etc) but I managed to change them by myself - so go figure how BMW is
authorizing dealers! It's a real shame for such a highly regarded brand
(or *was* it?).

Mike.
 

adrean8j

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#2
Mike where in Europe are you? The BMW dealers in my area seem to be pretty knowledgable but there are other alternatives. SMG has gotten better from what i have read and heard...yours seems to be one of the first generation SMG cars.....it would seem that when you are driving the car cold that the fluid in the transmission is more "viscous" and could cause the timing to be a little off...but that is just a guess...i think there are some threads on here concerning the SMG problems though...I have to look...
check here: http://www.bmwboard.com/forum/showthread.php?t=18278&highlight=smg
but this one is the most pertinent: http://www.bmwboard.com/forum/showthread.php?t=4150&highlight=smg+problem
 

Michael K

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#3
Thanks a lot for your input Adrean. I'm located in Romania, and the main dealer out here is neither knowledgeable nor charaterised by seriousness... It appears to be overhelmed by orders and prefers to leave you hanging or overlook issues he considers "not so important". He's not serving us BMW customers I guess, he's just making money and since there is no alternative in my city (yes, he's the only one in Bucharest, the capital city with 3 milion people and plenty of BMWs...) then all I can do is investigate by myself. Not that I don't like it, but this way I don't know if I will really manage to have it fixed.

Your explanation is extremely interesting, I've personally never thought of this! Just done a thorough test today and realized that there are slight hesitations *exactly* when (I guess) the hydraulic system presses/depresses the clutch. For example, if I engage "cruise" (the pseudo-automatic mode) then when an upshift is performed I can feel for 1 second *before* the actual shift is executed and 1 second after some hesitations which are not done in a continuous manner (that is, I can feel some small but perceptible shakes, 2-3 per assumed clutch operation).

I will take a look at the two URLs you enclosed - thanks a lot so far!

Mike.

adrean8j said:
Mike where in Europe are you? The BMW dealers in my area seem to be pretty knowledgable but there are other alternatives. SMG has gotten better from what i have read and heard...yours seems to be one of the first generation SMG cars.....it would seem that when you are driving the car cold that the fluid in the transmission is more "viscous" and could cause the timing to be a little off...but that is just a guess...i think there are some threads on here concerning the SMG problems though...I have to look...
check here: http://www.bmwboard.com/forum/showthread.php?t=18278&highlight=smg
but this one is the most pertinent: http://www.bmwboard.com/forum/showthread.php?t=4150&highlight=smg+problem
 

Michael K

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#4
Ah, forgot somethign that might me important: the described behavior (small shakes 1sec before + 1sec after upshift) happens with car warmed up as well.

Michael K said:
Thanks a lot for your input Adrean. I'm located in Romania, and the main dealer out here is neither knowledgeable nor charaterised by seriousness... It appears to be overhelmed by orders and prefers to leave you hanging or overlook issues he considers "not so important". He's not serving us BMW customers I guess, he's just making money and since there is no alternative in my city (yes, he's the only one in Bucharest, the capital city with 3 milion people and plenty of BMWs...) then all I can do is investigate by myself. Not that I don't like it, but this way I don't know if I will really manage to have it fixed.

Your explanation is extremely interesting, I've personally never thought of this! Just done a thorough test today and realized that there are slight hesitations *exactly* when (I guess) the hydraulic system presses/depresses the clutch. For example, if I engage "cruise" (the pseudo-automatic mode) then when an upshift is performed I can feel for 1 second *before* the actual shift is executed and 1 second after some hesitations which are not done in a continuous manner (that is, I can feel some small but perceptible shakes, 2-3 per assumed clutch operation).

I will take a look at the two URLs you enclosed - thanks a lot so far!

Mike.
 

Michael K

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#5
OK, I read the two pages you pointed me to, however I must underline it's not that "lag", "nose dip" etc what I'm complaining about (I think I understand somehow how this system works and I personally consider these two issues quite normal). What I don't get is why that trembling should be felt during the presumed clutch operation... and could an uneven clutch components wear be accused on a 66,000 km mileage car?

Michael K said:
Ah, forgot somethign that might me important: the described behavior (small shakes 1sec before + 1sec after upshift) happens with car warmed up as well.
 

thebrit

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#6
I have had the same thing happening in the lower gears since my car was new. I assumed this was normal. I have a 2004 325i with SMG.
 


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