Not joined yet? Register for free and enjoy features such as alerts, private messaging and viewing latest posts and topics.
Rhythmic vibration/resonance under light acceleration
-
- Newbie
- Posts: 2
- Joined: Wed Aug 10, 2016 6:56 pm
Rhythmic vibration/resonance under light acceleration
My Z4 (35i with DKG) produces very strong vibrations under acceleration or driving up-hill. This only happens with a low RPM of the engine, so for example driving 90 km/h on the highway and then accelerating to 110 km/h on the cruise control.
The vibrations are rhythmic and cause a strong buzz throughout the car (comparable to driving over road markings while changing lanes on a highway). The vibration only happens during light/medium acceleration or driving up-hill on the cruise control, mostly when in the D7 gear. It immediately disappears if I shift down manually or accelerate harder to cause a down-shift. There are no vibrations when driving under normal circumstances (e.g. city traffic or cruise control on the highway).
What do you think it could be? I've had the hardy-disc (flex disc) checked visually and looks fine. Also no errors when reading out the diagnostic log of the car. Further, the rear tires are almost gone but still have about 2-3mm left. I've been to a BMW shop and they did a test drive, confirmed the problem, but have no immediate idea. Before spending way too much on diagnosing, I'd like to see if someone here has an idea.
Could it be:
- worn clutch plates of the DKG?
- wheel bearings?
- rear diff?
- something inside the gearbox itself (as it's only in the 7th gear)?
- bearings of the drife shaft?
- worn rear tires? (but wouldn't that then be a constant vibration, not just when accelerating lightly?)
Many thanks for your expertise here!
Cheers,
The vibrations are rhythmic and cause a strong buzz throughout the car (comparable to driving over road markings while changing lanes on a highway). The vibration only happens during light/medium acceleration or driving up-hill on the cruise control, mostly when in the D7 gear. It immediately disappears if I shift down manually or accelerate harder to cause a down-shift. There are no vibrations when driving under normal circumstances (e.g. city traffic or cruise control on the highway).
What do you think it could be? I've had the hardy-disc (flex disc) checked visually and looks fine. Also no errors when reading out the diagnostic log of the car. Further, the rear tires are almost gone but still have about 2-3mm left. I've been to a BMW shop and they did a test drive, confirmed the problem, but have no immediate idea. Before spending way too much on diagnosing, I'd like to see if someone here has an idea.
Could it be:
- worn clutch plates of the DKG?
- wheel bearings?
- rear diff?
- something inside the gearbox itself (as it's only in the 7th gear)?
- bearings of the drife shaft?
- worn rear tires? (but wouldn't that then be a constant vibration, not just when accelerating lightly?)
Many thanks for your expertise here!
Cheers,
-
- Lifer
- Posts: 8202
- Joined: Tue Oct 26, 2010 2:52 pm
Rhythmic vibration/resonance under light acceleration
Imho if this is only 7th gear related it's an issue with the gear. Not clutches or anything else. That's an IMHO as I'm not able to test the car.
Take it to a specialist for diagnostics.
Take it to a specialist for diagnostics.
-
- Newbie
- Posts: 2
- Joined: Wed Aug 10, 2016 6:56 pm
Rhythmic vibration/resonance under light acceleration
Hi Maniac, thanks a lot for the reply. I've been to a BMW dealer and they did a test drive, confirmed the problem, but have no immediate idea what it could be. They have proposed to keep the car and take it 'home' with them so they can drive it for an extended time and try to isolate the vibrations. I'm guessing this will be an expensive quest to find the problem and start (randomly?) replacing parts...
That's why I'm trying to gather some ideas before hand and see if the problem can be scoped down based on other Z4 owners' experience. Thanks again!
That's why I'm trying to gather some ideas before hand and see if the problem can be scoped down based on other Z4 owners' experience. Thanks again!
-
- Lifer
- Posts: 8202
- Joined: Tue Oct 26, 2010 2:52 pm
Rhythmic vibration/resonance under light acceleration
Don't let them fiddle with the DCT, if they think it's that then have the entire thing replaced.
-
- Member
- Posts: 53
- Joined: Fri Jul 26, 2013 7:32 am
- Location: Espoo, Finland
Rhythmic vibration/resonance under light acceleration
I got this also (like everything else). Does anyone know what seems to be the problem?
I have HPFP and injectors replaced in last 6 months.
I have HPFP and injectors replaced in last 6 months.
- R.E92
- Senior Member
- Posts: 1644
- Joined: Wed Dec 04, 2013 10:10 am
Rhythmic vibration/resonance under light acceleration
It's because you are putting huge strain on the engine. High load, low rpm and a high gear is the worst thing you can do.
It wouldn't expect that to happen on a stock 35i though, unless your car has been tuned?
If the car is stock then I would also be tempted to investigate the ignition system. A bad spark plug or coil would cause issues like that.
It wouldn't expect that to happen on a stock 35i though, unless your car has been tuned?
If the car is stock then I would also be tempted to investigate the ignition system. A bad spark plug or coil would cause issues like that.
-
- Member
- Posts: 53
- Joined: Fri Jul 26, 2013 7:32 am
- Location: Espoo, Finland
Rhythmic vibration/resonance under light acceleration
It's stock 2010 35is.R.E92 wrote: ↑Wed Nov 22, 2017 1:20 pm It's because you are putting huge strain on the engine. High load, low rpm and a high gear is the worst thing you can do.
It wouldn't expect that to happen on a stock 35i though, unless your car has been tuned?
If the car is stock then I would also be tempted to investigate the ignition system. A bad spark plug or coil would cause issues like that.
Well coils haven't (yet) been replaced.
-
- Lifer
- Posts: 8202
- Joined: Tue Oct 26, 2010 2:52 pm
Rhythmic vibration/resonance under light acceleration
A bad spark could cause rhythmic vibration in 7th gear only?R.E92 wrote: ↑Wed Nov 22, 2017 1:20 pm It's because you are putting huge strain on the engine. High load, low rpm and a high gear is the worst thing you can do.
It wouldn't expect that to happen on a stock 35i though, unless your car has been tuned?
If the car is stock then I would also be tempted to investigate the ignition system. A bad spark plug or coil would cause issues like that.
- R.E92
- Senior Member
- Posts: 1644
- Joined: Wed Dec 04, 2013 10:10 am
Rhythmic vibration/resonance under light acceleration
I've always found that any weakness in the ignition system will show itself at high load and low RPMs. That's putting maximum stress on the engine.Maniac wrote: ↑Wed Nov 22, 2017 9:17 pmA bad spark could cause rhythmic vibration in 7th gear only?R.E92 wrote: ↑Wed Nov 22, 2017 1:20 pm It's because you are putting huge strain on the engine. High load, low rpm and a high gear is the worst thing you can do.
It wouldn't expect that to happen on a stock 35i though, unless your car has been tuned?
If the car is stock then I would also be tempted to investigate the ignition system. A bad spark plug or coil would cause issues like that.
The rhythmic vibration could be the engine retarding timing after sensing minor knock in a cylinder. The description of a buzzing or vibrating sensation fits with what I've experienced in the past when I've set the car into manual and floored it while in 7th at very low revs.
Using a tuning tool to take a log of the engine parameters would be the most helpful as you should see the ignition timing take a huge dump if it detects a problem.
On any other car i'd be looking at the drivetrain. Something like the DMF going bad. But with the N54 you have the big 3, Injectors/Plugs/Coils, that cause 90% of the issues.
-
- Senior Member
- Posts: 2552
- Joined: Fri May 26, 2017 3:40 pm
- Location: Plymouth
Rhythmic vibration/resonance under light acceleration
Can you upload an audio recording of the problem?Dantor wrote: ↑Wed Aug 10, 2016 6:58 pm My Z4 (35i with DKG) produces very strong vibrations under acceleration or driving up-hill. This only happens with a low RPM of the engine, so for example driving 90 km/h on the highway and then accelerating to 110 km/h on the cruise control.
The vibrations are rhythmic and cause a strong buzz throughout the car (comparable to driving over road markings while changing lanes on a highway). The vibration only happens during light/medium acceleration or driving up-hill on the cruise control, mostly when in the D7 gear. It immediately disappears if I shift down manually or accelerate harder to cause a down-shift. There are no vibrations when driving under normal circumstances (e.g. city traffic or cruise control on the highway).
What do you think it could be? I've had the hardy-disc (flex disc) checked visually and looks fine. Also no errors when reading out the diagnostic log of the car. Further, the rear tires are almost gone but still have about 2-3mm left. I've been to a BMW shop and they did a test drive, confirmed the problem, but have no immediate idea. Before spending way too much on diagnosing, I'd like to see if someone here has an idea.
Could it be:
- worn clutch plates of the DKG?
- wheel bearings?
- rear diff?
- something inside the gearbox itself (as it's only in the 7th gear)?
- bearings of the drife shaft?
- worn rear tires? (but wouldn't that then be a constant vibration, not just when accelerating lightly?)
Many thanks for your expertise here!
Cheers,
Go for simple things first, check your tyres are all good, wheels not warped. I have a ford focus (barf) for work, I had a new cheapo tyre fitted and had these symptoms. as the tyre was twisted on the rim!
Mark
Plymouth
E89
35i
Carmine Red
Black leather
Plymouth
E89
35i
Carmine Red
Black leather
- patriot66
- Lifer
- Posts: 3478
- Joined: Sun Jan 11, 2015 2:59 am
- Location: Mawdesley, Lancashire
Rhythmic vibration/resonance under light acceleration
Sounds like harmonic resonance through the chassis of the car because the engine/transmission are under heavy load
That's all. It's the cars way of saying "Please change down so my revs rise and I can spin more freely!"
That's all. It's the cars way of saying "Please change down so my revs rise and I can spin more freely!"
Sterling Grey '03 2.5i SE / Infinitas Supercharger / S.M.G / Hardtop / Gloss Black 162s / Bilstein B4s / 3.0i Brakes / DLV De-Cat & Silencer / Rebuilt VANOS / Sonar 2Xcite Lights / Carbon & Alcantara Trim / M-Sport Seats / ...& Side Covers !