Vibration. Hate to ask but...

[Anony Mouse]

I am at a loss. I'm beat tired at the moment so please excuse me if I fail to include some pertinent information.

I am getting a vibration which begins at 2k rpm, and intensifies as the revs climb. The vibration is enough to put in a slight hum in the glass and mirrors, almost as if I had subs going. It can be felt a little in my feet and hands, mostly in the bottom of the seat and side of the tunnel though, and is audible enough to cause a little pucker. It feels very much like sitting in the next room over from a big old school air compressor.

As far as I can tell there is no discernible change in the severity being under load or not. It happens equally on the road and sitting in my driveway on jackstands and in neutral. Bare in mind it makes this vibration in nuetral, and in the air on stands, while the transmission and driveshaft and differential are entirely immobile.

The car is a 1992 e30 325i Vert. Original m20/getrag combo. Predating this issue the car is lowered on Ireland stage 3 springs and billy sports. Ireland street camber plates and sway bars all around. M3 offset CABs. Mechanical fan delete, Miller AFM elbow, K&N Cone filter. UUC DSSR, Z3 short shifter. 2.9 LSD. 17x7.5" Kosei K1s, otherwise stock unless I've lapsed on something. I know some of that probably pertains in no way to possible problems but I plays it safe when beseeching the Gurus.

The vibration became noticeable immediately after replacing my driveshaft (and guibo), I replaced them because a CSB blew up on me. However it isn't the driveshaft, the vibration is unchanged in or out of gear, and moving or stationary. In the process of troubleshooting this I have installed Condor speed shop solid mounts on the tranny and motor. I have gone through my exhaust one end to the other and see no contact with the body, all exhaust mountings are intact except the funky crescent shaped one between the tranny and the hangers at the very rear. I also did spark plugs and since I was in there and it was about time I switched to green top injectors. In the process of installing the injectors I went through all my vacuum lines and they seem fine and I can detect no intake leaks. I cleaned my AFM and ICV while I was at it. There is no discernible change other than all the solid mounts transfer said vibration much more efficiently than the bad ones that came out.

Now the car starts fine everytime, doesn't overheat, no loss of power, no smoke, the only other thing that seems a touch off, she seems like she might be running a little rich, but its not bad and probably just the green tops settling in.

My hope is that one of you fine folks has witnessed or expedrienced this particular gremlin before and can shed some light on the subject, or at the very least suggest something I haven't thought of or found from googling the f*&^ out of the issue already.

Thanks in advance.
Mouse.

[Chriskbmx]

its the solid motor mounts causing the added vibration, they are ment to transfer instant response, so they transfer the vibration as well.

[amcink]

its the solid motor mounts causing the added vibration, they are ment to transfer instant response, so they transfer the vibration as well.

Agreed. Motor mounts

[Anony Mouse]

Motor and tranny mounts were after the vibration began. I wanted to eliminate the possibility of the old beat up mounts as a cause.

[DIIRTY-30]

Motor and tranny mounts were after the vibration began. I wanted to eliminate the possibility of the old beat up mounts as a cause.

Swap over to OEM rubber bushings, and tighten everything down. See if your problem persists. I have solid mounts and have slight vibrations, especially in upper RPMS. Mine aren't nearly as bad as yours, but then again solid mounts are far from stock comfort. Double check your front sway bars and bushings also, my friend had an issue when the tab snapped..

Hope you solve your issue, let us know.

:

[jlevie]

The solid mounts will make the problem worse, but since the vibration was present before the mounts were installed they aren't the cause. And because the vibration is present when the car is on jackstands and the transmission in neutral, the drive shaft, differential, and wheels aren't the cause. That leaves just the engine as the source. Mechanical possibilities include the harmonic balancer or the flywheel/clutch. But it could be that the engine isn't firing equally on all cylinders. Holding the engine at 3000rpm for a few minutes and checking the temperature of each header might diagnose that possibility.

[603Racing]

You said, "a CSB blew up on me". How severe was this? Did other things break or come apart? I'm thinking something along the lines of what Jim touched on... something with the flywheel/clutch or with the tranny (it does have a few parts that rotate while in nuetral). Is it a harmonic vibration when holding at a steady RPM or is it a flat vibration? By harmonic vibration, I mean does the vibration seam to pulse at a steady RPM?

I've also seen an e30 that was in an accident and the car ended up with a bent crank/harmonic balancer. It created an odd vibration that was discovered by seeing a visible wobble of the harmonic balancer. The owner repleaced the balancer and the wobble was still there, which was caused by the bent crank. I doubt you have a bent crank, but take a look at the balancer while the car is running.

[Anony Mouse]

I say blew up in the sense that it failed and was gutted, it fell apart. It failed slowly over the course of two or three days. B.A.R. sent me the wrong drive shaft first go round, so the car sat for close to a month while the driveshafts went back and forth. After the correct driveshaft was installed and I fired her up for the first time and I got the vibration. If I'm getting your meaning of harmonic, I would say no. It isn't a hum, and it accelerates as the engine does. I start to feel/hear it around 2k, and around 6k its rapid enough to be hardly noticeable, it feels like the result of something weighty spinning off balance, again no loss of power no overheating she seem to be running fine.

I'm wondering if in the process of putting the new driveshaft, and subsequent motor and tranny mounts in. I may have misaligned the drivetrain. Do you guys think if the motor and tranny were somehow askew I would get a vibration sitting still, out of gear, and on jack stands? If so how would you go about correcting that, is there measurement I can take in regards to motor/tranny relative angle or something?

[jlevie]

Misalignment of the driveline won't cause a vibration when the car is on jack stands and the transmission is in neutral. That has to be the engine.

[JohnH]

But it could be that the engine isn't firing equally on all cylinders.

I have been suffering similar symptoms to the OP, vibration increasing with revs (plus seemingly running a bit rich). Jlevie got me thinking, so I checked the plugs and although all of them showed some sootiness one of them was worse. I replaced the 415 green top injectors with the original 715 blue tops, and guess what. Its now running as smooth as silk. Worth a try.

[Anony Mouse]

Misalignment of the driveline won't cause a vibration when the car is on jack stands and the transmission is in neutral. That has to be the engine.

Yeah this is what my gut tells me. Ignition? Maybe rotor and cap?

[jlevie]

Ignition, injectors, or mixture could be causes.

[Anony Mouse]

Guess it'll be fuel filter, FPR, HT wires, rotor and cap. Hmm, what about CPS, think that could create this sort of scenario?

[bmwman91]

I'd do a compression test on each cylinder first. I'm sure you know how to do it, but just in case you do it with a cold engine and all spark plugs removed. Just unplug the fuel injector harness.

If those numbers check out evenly, I'd replace spark plugs next. If not that, then MAYBE it's the plug wires. If not that, maybe dizzy contacts? If all else fails, maybe it is an injector.

[Anony Mouse]

Did a comp/leak down not too long ago and it was fine. Plugs and injectors are new.