Engine vibration

humps

A2OC Donor
After spending more motorway miles in the weekend I'm confirming what I have discovered after installing the FSDs. With a new more comfortable ride, I'm getting strange vibration at between 72-85mph. It becomes noticable from 72mph and at 80mph, it shakes my steering wheel quite badly and becomes less as speed goes higher. However, it disappears when at 90mph or above. For my 1.4 petrol, this is right between 3000-4000rpm. The other observations I have are:

1. the vibration only comes on when I accelerate between the speed range mentioned. The higher the rate of acceleration, the more noticable the vibration.
2. vibration is less noticable when at constant speed
3. no vibration when my foot is off the throttle, even at 80mph.
4. no vibration between 1st to 4th gear, it only vibrates when in 5th gear and at that (engine)speed
5. The vibration comes through the steering wheel, the cabin and is noticable by passenger as well.
6. It reminded me of how the car vibrates when I drove towards the max speed.

I'm slightly concerned, this kind of vibration can be any good. Does anyone have any idea?
 
If it wasn't for the fact that you say there is no vibration, other than when you are accelerating, I'd say that your tyres had been put back incorrectly, so that the axels were out of balance.

Other than that, I'm none the wiser!

Cheers,

Mike
 
Hi humps
My best guess would be there is a high speed misfire or injection problem on one cylinder which is causing the engine run rough under full load.

Cheers Spike
 
hi humps
if you rember you asked us to change your wheels front to back could one of your tyres be ovel and when on the back dident show this vibration up
get them changed back and see if the vibration goes away

when i took maddys car fot its mot it has got ovel tyres on the back they are michlin pilots as well

cheers
robin
 
robin said:
hi humps
if you rember you asked us to change your wheels front to back could one of your tyres be ovel and when on the back dident show this vibration up
get them changed back and see if the vibration goes away

when i took maddys car fot its mot it has got ovel tyres on the back they are michlin pilots as well

cheers
robin

I might give it a go and see. But this was my first thought, oval tyres/wheel/uneven, but this should cause vibration at the same speed regardless of whether my foot was on the accelerator? I don't have much idea, but Spike's suggestion sounds cloest to the problem since I only get the virbration when accelerating... I don't suppose an overdue cambelt change have something to do with this?
 
Vibrations under acceleration

Hello Humps,

I'm experiencing a very similar problem. I sincerely doubt that it has anything to do with the belt.

Have you got an answer as to what was causing this vibration? I've got some indications that it might be faulty bushings on the front anti roll-bar.

Listening closer to the sound of the vibration it seems to me that a cylinder is misfiring under load just as Spike suggested.



/Patrik
 
Hi Guys,

Vibration through the steering at a "fixed" speed, which smooths out if you drive through it is the classic indicator if wheel balance problems.

Swap front to back for diagnosis (speed should change!) or just go and get 'em rebalanced!

ScotAlan
 
Hi, the vibration has been gradually 'lessen' over time! So it must be the tyre! Last time I was on the motorway two weeks ago, the vibration was not very noticable, I was very happy.

Well, I'm picking up my car later today after a cambelt/clutch change (which suffered a blown manifold at the bottom of the engine that took a week to fix). I'll get to drive on the motorway, so I'll check back.
 
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