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2002 325i pulls unevenly

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...

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.

Reply to
Mike
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Forgot to mention something that might be significant: when the car warms up, the problem apparently goes away.

Reply to
Mike

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?

Mike,

I read both of your posts (excerpted above). Why do you suspect the problem is in the driveline (clutch, SMG, etc.) and not merely the engine stuttering due to a lean condition? What happens if you leave the car in one gear and accelerate from a low rpm? If you still get the herky jerky, then the problem is not in the driveline. If nothing, then perhaps you are on the right track.

If the problem actually is the driveline then I would suspect a warped or unevenly worn flywheel and/or pressure plate.

Reply to
Malt_Hound

Thanks alot Fred for yoru input. 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). This happens after the warm up as well. So I guess it's more like something concerning the clutch, what do you think?

Mike.

Malt_Hound wrote:

Reply to
Mike

I am not an expert on SMG, but it sounds possible the clutch is slipping unevenly indicating warped or uneven surfaces to me. Why not run this by a dealer and see what they say. It should not cost you anything for a quick analysis...

You are certain that this is not due to the engine control part of the shifting program, right? Obviously the program needs to let off the throttle and re-apply it in the course of shifting.

Reply to
Malt_Hound

Hmm... You *could* be right with this one, I overlooked this possibility, thanks for the idea.

Do you happen to know, > Mike wrote:

Reply to
Mike

Yes, it will be smooth, but the power will also increment pretty dramitically as you accelerate.

That all sounds pretty normal to me. Power below 2000 rpm is pretty low and climbs rapidly with rpms. With BMWs variable valve timing (VANOS) there is sometimes a "kick" when the VANOS solenoid engages, but that is up around 3500-4000 rpm.

Reply to
Malt_Hound

If it's pulling unevenly it sounds like a misfire of some sort. Flooring the throttle at that RPM isn't going to produce much 'oomph', but it should still be smooth.

Have you had a diagnostic done?

Reply to
Dave Plowman (News)

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