Fabmaster911

My wife has a 1997 A6 Quattro that is having issues. We have owned the car for just over a year and it has had a bit of trouble with hard starting since we got it but it hasn't been a real major issue. The other day she was driving and it started to run real rough and lost so much power it was undriveable. It still would idle okay, had good oil pressure and temp was also normal. I got the car home and started to try and figure out the problem. The engine had kind of a ping sound up top and then a second ping type sound joined in. It is definetely not the tick like a lifter makes or a deeper thunk like a rod. It actually sounded like there was something on top of the piston. I fully expected to find a timing belt issue and bent valves but the timing appears to be good as far as I can tell and the compression is between 125 and 135 on all the holes. I have pulled the intake off and the tops of the pistons all look good as far as damage. Of course I can only see what I can see through the spark plug holes. The odd thing is that all of the pistons have a layer of carbon on the top except the number 2 hole. The top of this piston is shiny and clean as if the injector has just been blasting it or something. I've done a fair share of turning wrenches in my day but that was mostly pre injector days. I am wondering if anyone has seen this or if it's possible for injectors to fail and make this noise. I will also attach a picture of the plugs. The number 2 is the worst one. Any help would be greatly appreciated.

Today I opened up the intake and found this. Any ideas on how to fix it? I was hoping I wouldn't have to pull the heads but now I think I'll have to. I did find parts of the screw in the plenum but not enough to account for the whole thing.

grillage

Is the number 2 plug the blacker one in the center of the first picture?

What would happen to that screw fragment? I'd think it wouldn't make it all that far from there. Might be sitting on top of the piston.

Have you tried a magnet in the plug holes? You might get lucky and find all the parts in there.

Otherwise it might make it all the way to the cats?

Fabmaster911

Yeah the number 1 & 2 are darker than the rest. I have new plugs and wires and I also bought new injectors so hopefully that will solve that issue. How about using steel rivets to secure that plate back down. Any ideas?

CRAZY_RUSSIAN

did it come out or did it brake off? i would not use a rivet, find the correct screw at your local hardware store and put some lock tight on it.
this would also be good time to get the intake VAC cleaned

Fabmaster911

One was completely gone but I found most of it in the plenum and the other was just sloppy loose. The problem is that the threads are gone in the shaft and the shaft isn't big enough to oversize the holes.

hubturn

Had the same thing happen on a 12.5 hp mower engine except it was the screw from the carburator butterfly valve. The noise was as you described. All I found inside the cylinder was the screw head. The rest seemed to have been consumed. Gotta be a pretty high temp in the cylinder and the screw can't be made of that high quality of metal to survive that torture intact. Maybe you got lucky and no cylinder wall damage. This is when a boroscope would be nice to have. You open up one head to take a peek and suddenly you're into the "while I'm there" bag of worms.

Lago Blue

I believe that very few individual parts are available for the I/M, other than gaskets and the adapter for the ISV. IIRC WRT that particular screw VAP ordered some from Deutschland precisely to get one strong enough, vs the perhaps softer garden variety available locally.

A second manifold (cheap at the wreckers) will give you 12 chances to carefully file/grind & remove it's proper screws, a spare FPR etc., and give you something to clean and trip over until you get around to doing the "incomplete" manifold workshop (concentrates on capturing engine vacuum, EGR passage polish and injector port matching the heads); or the original workshop (see link).

http://www.12v.org/audi/imworkshop/

It is an interesting way to de-carbon your cylinder, perhaps what is left is small enough that it is just an annoyance and will find it's own way out? Since the piston-top is so clean, and slopes downward, if the piston was near TDC, could you fit a small magnet in the plug-hole to fetch the remnants at the piston-tops lower edge?

grillage

I happen to have an IM on ebay right now...

http://cgi.ebay.com/ebaymotors/ws/eB...m=330576380582