# B8 S5 Magnesium manifold problems after carbon cleaning



## knctrnl (Aug 5, 2018)

I have a 2008 S5 with the magnesium intake manifold. I am at 70,000 miles and decided to do a carbon cleaning.

I know someone who is a mechanic at the local VW dealership and has had training on Audi. 
He said he would do the cleaning and started work a couple of weeks ago. 
Once the intake manifold was removed he removed the dividers and cleaned the intake ports with brake cleaner. He said this is the exact process VW uses. When he was done the ports still looked like they had not been touched. 
I went and bought a media blaster and cleaned them properly with walnut shells. 
See images. First picture is of intakes after the supposed VW procedures for carbon cleaning. Second picture is of ports after walnut blasting.
Several days later he came back and did the assembly. (manifold flaps were only wiped down as I was scared to get wallnut shells in the intake manifold and didn’t know how I would clean it out.)

Once everything was back together I was getting random misfires, low fuel rail pressure and manifold flaps stuck open and closed.

The VW tech came back and after investigation found that he had used his electric driver to tighten the manifold bolts and the battery was low and did not provide any torque so I guess the manifold was moving around and loosing vacuum. 

After tightening the bolts we were still getting CEL and codes that I cant recall at the moment but I know they included flaps, low fuel rail pressure and random misfires.

He decided to take the manifold back off and check everything again. 
This time he noticed that he put the intake port dividers in upside down. This was keeping the intake manifold flaps from cycling fully. 
These were put back in properly and reassembled. 

Once everyting was back together I was still getting CEL with random misfires and low fuel rail pressure, but no flaps stuck. I was noticing more misfires on cylinder 2 and 4. 

My plugs and coil packs are 2 months old but I decided to pull the plugs and change them anyway. Plug in cylinder2 smelled of fuel so I started to suspect leaking injector. 

After plug change everything stabilized to only high misfires on cylinder2 and cylinder disable. 
I changed plug and coilpack from cylinder 2 to cylinder 1 and still got misfires on cylinder 2 and cylinder disable. 
I was also still getting low fuel pressure but this went away after a bit of time. 

At this point I decided to install new injectors on cylinders 1-4 myself.

I removed the intake manifold and noticed during this process that the ground bolt for the injectors 1-4 was very loose, The clip that attaches to the top Variable Intake Manifold Runner Motor is broken (note that this motor does cycle properly when vehicle is started). The clip for the flap motor is gnawed up looking I guess from him trying to get it to release.

I replaced the injectors and reassembled. 

At this time I am not getting any misfires or any fuel rail pressure codes but now I am getting consistent 

Intake Manifold Flap; Bank 1 
P2006 - 001 - Stuck Closed
And 
Intake Manifold Flap; Bank 2 
P2007 - 001 - Stuck Closed

I have looked in basic settings for bank 1 and bank 2 and I can see the position change on bank 1 when I press on the linkage slightly. Bank 2 shows 0 position and does not change when I press on the linkage. I am not sure if this is a proper way to check this.

When I do the output tests and it gets to the portion of these flaps they do not move. They also do not move when the car is started.

Can anyone shed any light on this situation?

Are there any adaptations that should be ran?

I am about to take the intake manifold off again and try to clean carbon off the flaps on the bottom of it. 
Anyone have any tips in case I get any crap in the manifold plenum?


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## SDArteon (Jun 16, 2019)

knctrnl said:


> I have a 2008 S5 with the magnesium intake manifold. I am at 70,000 miles and decided to do a carbon cleaning.
> 
> I know someone who is a mechanic at the local VW dealership and has had training on Audi.
> He said he would do the cleaning and started work a couple of weeks ago.
> ...


Have the same Engine and did carbon cleaning myself - yes you have to be careful to put port dividers in correctly. I did that and still had the flaps stick. I just gently jostled the arms and the flaps started moving again. Also, this is a job that is time consuming, but straightforward and it needs some care to be taken - follow the torque sequences and the torque limit when pulling down the manifold - apparently it can warp and lead to sticking flaps. On the 2009 S5 Audi changed the design - I believe its not longer magnesium. Expensive part if one f’s it up, so take care if you are reading this post and intend to do DIy. Plan on 2 full days to do this job properly.

last thing about flaps moving the connectors are very tricky to plug back in to manifold and its possible the connector is not 100% seated correctly. If not that shpuld throw a fault code, but its worth checking.


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