Flashing coil light

Somerandomguy · #1 27th August 2012, 05:54 AM

After my accident earlier this year, i had a split turbo hose that was missed by the repairers. I took the car to holland immediately, and thats when the problem came to light with the flashing coil light wanring a couple of times a journey which was cleared by restarting the car. VSDS reported underboost.

I did about 1000 miles like that before getting home and replacing the offending pipe.

the coil light came on a few times a couple of days after fixing the pipe and VCDS this time reporting overboost and incorrect/missing adaption,and then maybe came on once every couple of weeks with the same errors after being cleared by rstarting the car again.

I am now in germany and thought i would stretch her legs, and seem to be able to get the fault to come on at 125mph (on the abahn). Have i damaged the turbo, or does it just need to re-learn the engine parameters? It seems to sound a little more tractor-y at low speed these days, so im getting a bit concerned.
Thanks

ainarssems · #2 27th August 2012, 07:51 AM

It could be sticking VNT mechanism on turbo, incorrectly adjusted VNT rod length or a problem with regulating system electrical or vacuum whichever you have on your car. It could be that VNT was all the time in one end position trying to increase boost when you had leaking hose and did not get exercised so now it is not moving freely to other end position. You cannot service it without taking turbo apart. Only thing you can do is go into basic setting on VCDS with car in idle, this will move VNT actuator from one end position to other. You should see pressure changing from 980mbar to 1080mbar or thereabouts as it moves. You can also observe actuator as it moves and check if it does travel full length and possibly help a bit if doesn't. Hopefully it will work OK once you get it moving. It should learn parameters while in basic mode as well.

Our A6 was overboosting as well and it had turbo replaced by previous owner. Not overboosting enough to get fault code but you could see it in logs. It is possible that old turbo died a premature death because of overboosting or it could be that it was fine before and new turbo's actuator was not adjusted perfectly. Anyway doing mapping I adjusted VNT control map to minimize overboost.

Somerandomguy · #3 27th August 2012, 07:17 PM

Cheers, ill give that a go tomorrow.

Somerandomguy · #4 5th February 2013, 06:15 AM

For the sake of completeness, and for the benefits of others whommay have a similar problem, i thought i would follow up on this.

The fault has persisted every week or two, first throwing the missing adaption/electrical fault followed by overboost if i accelerate at all. Took it to an audi specialist for a new water pump and alternator who found a long standing leak on intercooler pipe (other side to the one i fixed). He reckoned that it had been there for 60,000 miles or so and so was not a constant leak as there was an inch or so of gunge. Cleaned it all up and fixed the leak, and so far so good- looks looks i dont need a new turbo afterall