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
 
Hi there all,
keeping safe I hope.
Thanks again for all your input.
Defiantly NOT engine mount problem, I didn't think this would cause the problem but decided to swap mounts between 2 of my cars and problem still remains.
Haven't taken time to check for air in the fuel system/lines but I'm going to follow this as my main route to check.
The car has generally been running fine for the last couple of months (haven't used it much due to Covid lockdown) but as the problem did start to show signs of returning last week, so as before I took the car for a short drive to get it up to temperature then found a quiet road and ran the car for a period of 20-30 seconds at HIGH revs in low gear and when i got back home the problem had gone again. My thinking is that somewhere in the fuel system air is being introduced into the lines/pump which at lower revs cannot be pushed through the injectors thus the lumpy running at lower revs but possibly wouldn't affect too much at higher revs (hence still having reasonable power) but when ran at high revs for a longer period might force the air to atomise and pass through the injectors and remove the air lock.
Your thoughts please.

Few last questions - Does anyone have any experience on changing or repairing the fuel pump (if it is found to be causing the problem). Is this a specialist job? Any ideas of time and costing?

Thanks again everyone who has helped.
 

cheechy

A2OC Donor
So tandem pump repair kits are available but they are just essentially seal kits that assume the pump is working but just needs an overhaul.

New Bosch pumps can be had from buycarparts for around 100-120 quid last time I checked if thats also an option.

@depronman for sure has experience in changing pumps.
 

depronman

A2OC Donor
Is it a petrol or diesel ?
Assuming diesel then the tandem pump is the likely bet. Change for a Bosch pump but there are extra parts needed are needed if you have an bhc/atl


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audifan

A2OC Donor
As it is a BHC engine you will need a few extras if you use the far better Bosch pump. Another LUK will swap straight over. Just remember to get a good OEM quality gasket with the extra little traces of silicone on it. How old is the fuel filter, have you drained out the water? Check all the fuel pipes for deterioration as a tiny hole will allow air into the system. If you can replace the rubber hose that feeds the tandem pump with a length of clear and look for any bubbles up to the pump. Are there any signs of leaks around and below the tandem pump? Failing injector(s) or seals also a possibility.
 

dj_efk

A2OC Donor
I am probably overly “on a mission” about this subject at the moment, but I think your “least likely” cause could well be the culprit at that mileage.

Trust me, if you’ve been lucky enough to get to way over 200k miles on your original chain, tensioner and sprockets(!), they need replacing urgently! I’ll eat my hat if you tell me that it didn’t really need doing after!
 

depronman

A2OC Donor
I am probably overly “on a mission” about this subject at the moment, but I think your “least likely” cause could well be the culprit at that mileage.

Trust me, if you’ve been lucky enough to get to way over 200k miles on your original chain, tensioner and sprockets(!), they need replacing urgently! I’ll eat my hat if you tell me that it didn’t really need doing after!
I don’t disagree but unlikely to be the cause of intermittent rough running unless the chain is jumping teeth and causing the balance shaft to be out of sync then jumping again and going back into sync. I’ll pick the lottery numbers tonight if it’s doing that
Again just to confirm I think the chain tensioner are the least will be well worn and need changing ( just not convinced that it would /could cause this specific issue)
I did take an amf engine to 288,000 miles without the chain or guides being changed and it’s still running around clocking up more miles as I sold it locally but again I’m not recommending this course of action

Paul


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Thanks everyone.

Looks like a tandem pump to me. I've got access to a spare pump (fitted to a spare engine) are they a straight swap or do they need setting?

Hopefully going to have a look this weekend.
First thing change fuel filter (again) and check all fuel lines clips hoses etc. Find some clear hose and check for air in the fuel lines.

I reckon I'm going to have chain & tensioner changed as suggested. Any ideas of prices and would you recommend Audi or independent?

Not selling the car I've owned the car for 7+ years, best car I've ever owned and no intension of getting rid of it any time soon.
Had 4 so far (3 TDI and 1 FSI) managed to bring them back from spare/repair cars and sold them to family members. Managed to convince the wife to let me keep 2 (Just)
 

depronman

A2OC Donor
Assuming the same make of tandem pump the a new gasket and new bolts They are stretch bolt so single use
Make sure Ethan both cylinder head and pump are spotlessly clean else it will leak oil
If you needed to buy a new tandem pump the Bosch pump is far superior to the LUK but needs a modified spacer on the bhc and atl engines to make it fit the different induction pipe work used
Paul



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