A2 TDI violent shaking

Hi there, I have been a long time member of the forum but this is my first post.

I previously worked as a mechanic 1990-2000 at an independent garage so I have a reasonable understanding is mechanics.

I’ve owned and rescued 4 A2’s over the years. I still own my original A2 53 plate TDI engine code BHC now has 230,000 miles owned for 7 years with regular servicing and VERY few problems. About 3 months ago the car developed a problem while running at about 1500-2500 rpm where it shook slightly but didn’t seem to affect the performance. Slowly over the next few weeks it got SO BAD the whole car would shake violently. It doesn’t matter if I’m moving or parked, clutch in or out 1000 or 3000rpm.

Strange thing happened a week or so later when it seemed to disappear completely for about 1 week but recently it reappeared and seems to vary from shaking really badly to extremely badly. I have my own ideas of what may be causing this but would appreciate your advice and experience before spending too much time (of which I don’t have much spare).



My thoughts

No.1 - Worn balance shaft chain/drive sprocket that may have jumped teeth and become out of balance. (not sure if this is even possible) 230,000 miles and no history of chain replacement. This I consider is the least likely cause.

No.2 – Blocked injector (not sure how easy they are to remove)

No.3 – Faulty fuel pump (slight fuel residue on end of cylinder head but has been like this for years)

No.4 – Electrical fault. Either wiring loom or earth fault (I’m aware these can both cause problems)



I do have another TDI BHC 2004 that I could swap parts over with to check components if needed.

I have a cheap hand scanner and there are no faults showing and also no lights on the dash.

Thanks in advance.

Lee
 

audifan

A2OC Donor
I think the injector loom is failing. Balance shaft, would shake at all rpms. Blocked injector again all rpms and fairly constant misfire. Fuel pump while you probably would benefit from replacing it do not think so.
Unfortunately swapping the injector loom from one car to another will be a lot of work. Have the car scanned with VCDS although the loom probably will not show up. Intermittent rough running is a symptom of a failing injector loom.
 

Olerype

Member
Have you checked your 3 engine mounts (rock the engine with you hands or sprocket in eg the gearbox mount)?

Is engine mapped?
 
Hi there thanks for your input.
Engine is std (not mapped)
The vibration is throughout the Rev range now ( from just off idle to flat out)
Engine mounts are fine

I’m tending to think injector loom at the moment. Won’t swap from my other car as too much hassle. Does anyone know the loom part no.or best place to get one from. I’m thinking too risky using used part would prefer new if not too expensive.

thanks again everyone who posted.
 
Hi all, sorry it's been a while.

Found myself with a little time to spare this week with everything going on.
A few weeks back I purchased a new loom as suggested and replaced it yesterday and.........……..

Still the same.

I was fairly sure that the new loom would solve my problem but hey ho.
Once the loom was replaces and showed no obvious improvement I took the vehicle for a test drive.
while on my test drive I remembered a comment my wife made to me around the time the issue temporally disappeared. She said that she had driven the car really hard (lots of throttle and revs) and the next time she used the vehicle it appeared ok.
So basically I got the vehicle up to normal operating temp then ran the engine along a closed road FLAT OUT on the rev limited for approx 20-25 seconds in first gear. I took the vehicle home and its been fine without any problem since.
Does anyone have any further ideas? possible fuel pump problem? fuel system air leak or air lock?
The fuel filter was changed at last service but was approx 6 months before the problem started.

Thanks everyone for their input.
 

O07JESTER

Member
Is it possible it's the original tandem pump?.If it is very worn then maybe the pump is not delivering enough fuel in normal conditions.When I replaced my pump there was a noticeable difference on idling and responsiveness.
 

spike

Well-Known Member
When checking the engine mounts did you also look at the 'dog bone' mount which controls fore / aft engine rock - the one underneath the car

Cheers Spike
 
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