plova

I have just removed the intake manifold for my 01 A6 Avant (2.8l) and I am wondering if someone could recommend the best way to clean both the intake manifold and the intake ports. I am a bit hesitant to use something that is too harsh on the intake manifold as it is made of a plastic composite rather than some sort of cast metal composite. If someone has cleaned this type of intake manifold before I would appreciate a recommendation for the cleaner to use as I have seen that some have used carb cleaner in the throttle body but could find nothing for the manifold. The same goes for the intake ports. To be honest, the intake ports are surprisingly clean, simply some carbon build up at the top of the ports that taper down to 1/2" before the valves. For a car with 150K on the clock I thought the build up would be worse after viewing the problems with the larger 8 and 10 cylinder FSI (direct ?) systems after 8-20K. I know that the 2.8 has a different system but I guess I was expecting the worst. The build up is more or less "sludge like" but on the dry side. I also would like to know the best procedure for cleaning the ports. It seems that it would make sense to remove as much of the build up as possible before using any type of solvant. Also, if I can use a solvant, is there one that can be left in the ports that will break down the build up enough to have any residue pass by the valves and not hurt them.

The reason why I took off the intake to clean it was upon recommendation from a local Audi tech. I was having secondary air problems-insufficent flow (I can't remember the codes). I started by replacing all the hoses which didn't solve the problem. I then checked records from the previous owner. At one service the dealer recommeded changing the combi air valves, which I went ahead and did. Still had the problem. When speaking to a tech at the dealer he mentioned that it was probably the intake that had too much carbon build up in it as this was a common problem according to him. While there is more build up in the intake manifold it doesn't seem to me that it is enough to cause the air flow problem or any blockages. What I did notice as I was taking off the intake that buried back behind the intake was one more vac line that two of the hoses "T"ed into. The braided hose of course was shot and most likely the cause of the air flow problems as it was effecting both banks. The hose is larger than the other hoses and held on by clamps to the "T" and where it enters the intake manifold. I intend on posting this on the forum with some pictures after I finish to save someone else from having to possible do extra work. It was one of those "WTF: moments wondering why Audi didn't use a metal line at this point !

Thanks,


Jeff

plova

Just for reference the codes were 1423 and 1411 for the 2nd-ary air problem.