Engine Knocking

[Fordhom]

I've been reading this forum for a while, but have held off from posting until now.....

I bought my S3 in april of this year and have had a great time with the car since, pushing the mileage up to 118k from the 104k when I bought it. Other than some relatively minor problems all had been going well until Monday, when I was greeted my a nasty knocking noise when I started the engine. After some fun and games with the RAC man attempting to figure out how to tow the car it was taken to a garage in Cambridge. After some research they have discovered that the noise is caused by the no. 2 cylinder backfiring into the inlet manifold, and apparently this means sending the cylinder head off to some specialist is Soham, and may have been caused by running an old engine on unleaded.

I fear there's not much I can do about the problem itself except wait and talk kindly to my bank manager, but any ideas or at least comiserations would be appreciated! What I would like some practical advice on concerns another issue. The car needs some welding done on the chassis, which I've been putting off (I know I'm a bad person, but I just don't like the thought of being away from the car for very long). I've had some work done on the car at a great place in North Hertfordshire before, and was very impressed with their work, so was thinking of having the welding done there. I therefore have had the crazy idea of arranging to have the car moved to their garage (assuming they've got time to take me) and having the work done there during the time the cylinder head is being turned around. I'd then arrange for the cylinder head to be returned to them for refitting. If anyone here has any advice about the merits of this crazy scheme or could recomend any companies that could move the car for me it would be much appreciated!

[SLB]

I had one of the very first S3's from new and ran it on unleaded. I was informed the Cologne 2.9 V6's had hardened valve seats and I seem to remember seeing "unleaded" stickers on some car's fuel fillers, although that could have been the cat cars.

It's not BRG with black interior and driving lights is it? I can't see how they can blame unleaded for it, but it does soumd sick. Good luck.

[sotonS2]

SLB said:

I had one of the very first S3's from new and ran it on unleaded. I was informed the Cologne 2.9 V6's had hardened valve seats and I seem to remember seeing "unleaded" stickers on some car's fuel fillers, although that could have been the cat cars.

I think SLB is correct - AFAIK all 2.9 V6s run on unleaded. The cause of the problem probably lies elsewhere.

[Roy C]

sotonS2 said:

SLB said: I had one of the very first S3's from new and ran it on unleaded. I was informed the Cologne 2.9 V6's had hardened valve seats and I seem to remember seeing "unleaded" stickers on some car's fuel fillers, although that could have been the cat cars. I think SLB is correct - AFAIK all 2.9 V6s run on unleaded. The cause of the problem probably lies elsewhere.

Yep, although early 2.9s may need adjustment (the changeover was during S2 production - details in the Bible). S3c & S4 had the unleaded only stickers. Pre-cat 2.9s will run on either.

[Fordhom]

Thanks for the replies. It is indeed BRG with black interior, although think the extra lights are foglights rather than driving lamps as they illuminate with dipped headlights not full beams. Why do you ask? Your old car?

Anyway, have now given up on the crazy scheme of moving the car to get the chassis work done, will just have to survive a few extra days without my lovely car in a few weeks time!

Thanks again guys.

[z_chromozone]

Recutting the valve seat should not be much of a problem if that is what is wrong. Even heads with hardened seats can suffer problems. I have a golf head with the entire section between the valve seats missing on my bench at the moment.

If the inlet valve is not seating properly a compression test should show this up straight away. It may just be that it is not seating properly because the valve spring has bust. Hopefully it will not cost you too much to put right.

Welding of the chassis can be attempted with the body jacked up, which will save you £ and time. Have an ask around a couple of others have had that kind of work done.

All the best,

Z