chiefironbear

The first question i have is, are there upper and lower flaps on the S8 5.2L intake manifold? I might need to replace flaps so I'm told I might as well change lower ones since I'm already in there.
Second one is, should i change the plug and coil in a cylinder that I'm getting a random misfire? The car has 65,000 miles plugs were changed at 53,000. THX

mishar

Your first question is not really clear. Why do you think that you should replace flaps? If you are talking about flaps that change intake length than there is left and right set of them.

Your plugs are fairly new, but they can be faulty from the box. Coils and plugs are cheap. I would change both.

chiefironbear

Took S8 to indie shop and after doing the cycling of flap motors via VCDS i was told that they need to be replaced I've seen a few people end up doing the replacement under warranty, so i'm seekng any advice cuz the job is not cheap and I'm out of warranty.

mishar

There are upper and lower drive units. They are not that expensive here.

s4master1

lower flaps 079 103 411 Q aka partition flaps don't need to get replaced, they can be clean and reinstall.
if you having random misfire on one cylinder I suggest replacing that injector.
the upper flaps have potentiometers monitoring their position and if the shafts are sticky they will give you a fault.
while the manifold is out ask them to check the shafts for binding.

MP4.2+6.0

First, figure none of your "pages" actually has a 5.2, so we are crossing over from W12's and 4.2's, plus general experience.

You already have some good replies on the intake. Do make sure to figure out along the way if it is a true failure, or just a binding type issue that could be cleaned/lubed.

New idea though: read the emissions warranty very carefully to see if the intake operation is covered. Smog warranties often tie to parts (not) in general use at time the underlying laws came in. And of course there were always manifolds, but multistage is later in evolution. My experience is dealers and service depts don't really like to flag that warranty, but it's there if it applies.

Similarly on your coil pack by the way. And, I don't know about the S8 motor, but recognize rafts of Audis have been recalled for coil packs, including 4.2's and my W12. I got a complete new set of 12 courtesy of that recall. Check and see if your car had such a recall, and if it was done.

Meantime, besides a straight coil pack replace, the old diagnostic way (when coils cost more and if pretty easy to get at) is simply to swap the suspect coil to a different cylinder. If the problem faults move with it, it's the coil. If the misfire stays with the initial cylinder, it's something else like injectors, wiring or control electronics. By the way, if it could be the injector, do the obvious of running through a bottle of Techron--the big size for D3's. With an FSI motor it won't clean the intake valve any more, but at least it will help w/any possible injector issue. I always run through a bottle cycle per oil change, if not more.

chiefironbear

Thanks a lot guys for all your help car goes in this weekend 2/7/13 for manifold removal and diagnosis plus the other aforementioned issues. I will give an update as to the findings.