E30 318i M40 Engine vibration at 2500rpm

[chaz]

I've just bought a 89 E30 318i touring (UK spec) with the M40 engine and manual box, the general condition is good especially considering it's done 165k miles. I'm now working my way through all the known faults to make the car as good as I can get it.

I've known that since I bought the car a couple of weeks ago, it's had some vibration issues which I originally thought were related to the drive train ( as it's noticeable when accelerating through all the gears) . However on the way home today I realised that it is actually the engine which is causing the vibes, as the vibes are even present when the car is stationary and the engine revved.

Sitting in neutral if you slowly rev the engine up, the vibration occurs at mid rev range, peaking at around 2500rpm, then improving again higher in the rev range. At 2500rpm I can even feel bad oscillations through the seat and it's also quite audible, sounds like it's really oscillating any cables or panels down near the footwell. If you then depress the clutch and do the same increasing rev test, the vibration is still there but noticeably improved, especially the noise factor.

I'm thinking it could be an out of balance or worn or poor quality clutch, faulty/incorrectly fitted flywheel or vibration damper or even something to do with the input shaft toe bearing, or even the crank shaft such as worn main bearings or end-float? Whatever it is, when pressure is applied to the clutch, it seems to affect the vibes, so this implies to me that it's stabilising the crank or clutch asembly helping to prevent that vibration movement somewhere....

Any ideas what this could be? or how to better check it out? Are there any known problems like this, with this engine? I'll have a better look at the weekend, but I can see how this kind of problem might not be obvious by using eyesight alone.


Any help would be appreciated.

Thanks

Chaz (U.K.)

[winfred]

you will probably not get too many hits as most of us have never seen a car with a m40 motor as they never made it into the us. if the clutch effects it there may be a thrust washer problem, you can pry the crank forward and back with a big screw driver, pretty much if you can more then barely see movement it's bad. i have read bad things about m40s eating valve train parts but i can't really comment

[84318i]

same problem with my E30 1984 318i whenever at stand still with clutch pressed or not in gear or neutral it revs at about 1300 rpms and when driving revs up to about 2300 and then starts bucking and wont go past. My guess was in the electrical problems, i changed the plugs,dist,cap,rotar, and i am going to switch the wires. Now every once in a while it goes great still idles high but will rev past 3 through 4. I was looking for someone who knows A. how to change idle speed and B. someone who can figure out why it bucks at 2300 and won't go past sometimes and not others.

Another guess was i need a new battery but it seems fine. I have to get it checked out.

Maybe an ECU problem?

[BMWrestoration]

Dear Chaz,

You will find that the Pressure plate attachment plates have bent. If you remove the transmission to expose the clutch assembly, you will see three flat spring plates that attach the pressure plate to the plate housing. If the previous owner "dumped" the clutch too hard, these plates will bend. Once this has happened, the mass is no longer centered and will vibrate through all RPM ranges.

Good luck on the repair.

Regards,
Louis