Hello my fellow A4 owners....

My A4 is a late 2001 B6 on a Y reg plate, which makes it from the first batch of B6 A4s.

I first noticed this problem a year or so into owning my car - probably some time in 2004/2005. It was 3 years old with 15K on the clock when I bought it. In mileage terms, it would have had about 20-25K miles when I first noticed the problem. The car has now down about 78K miles.

I'm posting now because I've had some work done on the car that I would really have expected to have stopped this happening...

When code, the car idles nice and smoothly. After 7 to 8 minutes I stop at lights or a junction for example so the car idles, it will either start shaking or wobbling. It's not violent (now) and sometimes, these movements at idle won't even occur!

The rev needle sits perfectly still at 900 rpm and if I engage the rear demister, the shaking/wobbling stops and the idle is smooth again

The work I've had done includes a new injector in one of the cylinders - the air mass flow meter was replaced at the same time (my second now) and when the Air Con radiator was replaced due to a hole, the cam belt pre-tensioner was replaced. I've got new shock springs on the back and the front tyres are only a few K old.

When the injector was failing I would have a complete loss of power and sometimes, violent shaking at idle - I really hoped that this expensive work would finally resolve the issue.... Despite the shake at idle, the car drives like a dream - the trim is starting to show the age of the car but otherwise, you would't know!

I have thought about the engine mounts being at faullt but surely they wouldn't cause the shaking, they would just transmit the shaking?

Engaging the rear demister always stops the shaking - what on earth could the cause be?

What do you think?

Nathan

 

I'm really illiterate on diesels, but it sounds like when a coil or harness starts failing on a gas engine. I would scan it with a regular OBDII scanner to see if it gives any codes and go from there, sometimes there's codes stored even if there's no light on.

 

I also don't know anything about diesels but I agree with Dan1969. Go to an auto parts store and they should have an OBDII scanner that you can borrow. Get the codes then come back here and search. I've heard that a rough idle can be a Vac leak so check all of the check valves. There are a few of them and they fail quite often.

 

When the car had the last set of work (only a couple of weeks ago), they cleared all the fault codes and nothing new comes up - as far as the engine management is concerned... there is nothing wrong!