TDi violent shaking when idle

[nathanc]

Hi all

I've had my A4 Tdi 130 for nearly a year now and I have to say it is a superb car.

But, there is always a but. This problem is more noticeable in the warmer months as the engine heats up more quickly but let me attempt to describe the problem.

From cold (2hrs + stationary), the engine while noisey is smooth and as it should be. Then from 5 minutes and upto about 15 minutes after ignition, the car shakes violently when idle. Then after 15 minutes or so it is fine.

For example, I work in Slough and the first 10 minutes of my journey is stop start. Whenever I have to wait at traffic lights, the car shakes and wobbles from left to right.

If I increase the revs over 1K, the shaking just speeds up into a vibration.

Looking at the temperature gauge, it seems to occur around the 75 to 90 degree area.

Whenever I've tried to demonstrate it to a dealer, the car is too warm and doesn't do it.

Any ideas?

 

[technics100]

Mine does the same although only when I have my tuning box plugged in. I believe our cars have solenoids in the engine mounts that adjust the amount of damping required for each mount. If you could get a vag-com you would probably see it will throw a code... for the "engine mount solenoid sensor"

 

[imported_Lesr]

My TDi 130 A3 does the same thing - do they have solenoids in the engine mounts as well?

 

[nathanc]

I'm not really sure what a solenoid is - how would that contribute to the shaking?

 

[technics100]

the way the mounts work is that there is a fluid chamber with a plastic body in the middle of it, with small channel cut through it. this allows fluid from the top chamber, through the plastic body, to the bottom chamber. the bottom chamber is rubber lined and can deform under pressure. there is also an airway vented to atmosphere, with a rubber membrane separating the fluid from the atmosphere. a solenoid valve, controlled by the motronic, can open or close the airway.

below 1100 rpm (i.e idle), the engine vibrations are not enough to force fluid from the top chamber, through the passageway to the bottom chamber. the airway is open (solenoid valve open). the rubber membrane creates a soft cushion which absorbs the high frequency vibrations.

above 1100 rpm the soleniod valve is closed which blocks the airway and so "hardens" the mount (the fluid has nowhere to go). thus the mount is effectively solid.

the high frequency vibrations at speed are absorbed by the membrane (as in the idle case), while the more damaging low frequency vibrations cause the fluid to force itself through the chamber in the plastic body to the lower chamber, forcing the (lower) rubber chamber to distort - effectively absorbing the vibrations.

in this case i would suspect that the mounts are bad - possibly as simple as the connectors have been pulled off.

 

[nathanc]

Very interesting technics100!

Earlier, you mentioned plugging in a VAGCOM would probably display a soleniods related code... wouldn't the Audi "Engineer" servicing my car plug a VAGCOM in and check everything is okay anyway?

 

[technics100]

Not unless they were asked, they will charge you for the privilege...

Its just a thought because mine does the same and throws the following code.

Engine 17994 - Engine Mount Sensor Solenoid
Valves N144/N145 Short to Plus P1586 - 35 to intermittant

 

[nathanc]

My thoughts too...

I guess I'll have to take the car round the corner to Wheelbase in Hersham. I've read elsewhere on this forum that those guys are good.

 

[JSWD32]

Your Temp sensor on the rad might of gone, I had a similiar problem on mine and it turned out that the engine was being overcooled.

Regards

Jonathon

 

[Funkyfin2000]

Ive got a similiar issue with this. How much are the mounts? Do they come with the electrics (ie solinoids)