Intermittent serious vibration or misfire

[Paulgreg1]

I have a 51 plate galaxy tdi that has developed an intermittent vibration problem it has varying degrees of severity, it sometimes feels like the engine is going to jump out of the bonnet! There seems to be no pattern to it and there can be hundreds of miles between fits! Once it starts i have to stop and turn the engine off this mostly rectifies the problem but not all the time! It's also worse when i accelerate and eases when I take my foot off. Had it in the garage three times and it never misbehaves when he's got it! Anybody got any suggestions?
Thanks Paul

[insanitybeard]

Is it a fault that only occurs with the vehicle in motion/ in gear or does it happen when stationary as well? Do  any warning lights come on when it happens? Are you able to check for fault codes?

Purely semi-educated guesses on my part but it could be down to a mechanical issue, such as a failing dual mass flywheel, inner CV joint on the way out or maybe a wheel bearing.

Or, if it's electrical it could be to do with something like the injector wiring loom, I'm not sure if duff MAF sensors cause rough running or just loss of power.

Ideally you need to see if any fault codes have been stored first.

[Paulgreg1]

Yes only runs rough when in motion . There is no loss of power just the intermittent vibration problem . I have on your advice been back to the mechanic today to check the fault codes which showed a fault with the maf sensor .just wish he had hooked it up on one of my previous visits and before I had taken a horrendous jouney to the south of france and back !. I have replaced the sensor and fingers crossed its that simple !!

[Chrispb]

Hello and 

Maf sensor won't give vibration problems, you should be looking at drivetrain EG driveshafts wheel bearings steering joints.
Injector wiring loom can cause a cylinder misfire but this will throw up a fault code for a particular cylinder.

[Scorpiorefugee]

Hi,
I may be way off the mark with this but I had a similar problem on my 52 Gal. very intermittent, violent and very worrying. It had me totally puzzled until I got out one day and felt the heat coming from my OS rear. It appears that the brake pads were going into an oscillation. When it happened it was impossible to know where it was coming from because the whole car was shaking like a 10 times worse case of running on the warning bumps on the side of motorways etc. A new caliper and pads was the only cure.

[bigjeeze]

Scorpiorefugees post sound a likely culprit - but if not then why not check the alternator pulley? This may be failing and when it does it gives a horrendous vibration when the power steering is in operation.

[gregers]

clutching at straws here,
not the stabilizing bar about to shear by chance?