S4 B8 revving idle after thermostat replacement

[sheldon0]

Hi Guys,

I'm kind of at a loss at this point and was hoping I can get some good ideas what to check next. I screwed up something on the weekend when I replaced my thermostat and waterpump (it was overheating) but I cannot figure out what. The job itself went well, I labeled the vacuum lines accordingly and made sure that everything went back into the appropriate connectors.

Now when I start my car it revs up and down from 1100 to 1600. It almost sounds like it wants to die but it never does. I drove it around the block to see if I can get some codes - the only thing I got so far was P050A but no CEL.

I checked and re-checked all the vacuum lines, removed the Supercharger twice to make sure I didn't miss anything underneath but I cannot find the cause. I also replaced the coolant temp sensor on my first run but put the original back in after this issue started to see if that was the cause (unfortunately it wasn't). I sprayed brake cleaner around the vacuum lines and where they plug into but nothing changes the engine behavior so I don't think it's a vacuum leak.

I would be very helpful for any pointers.

[tryan100]

Did you maybe not get the crank case breather pipe lined back up under the supercharger?

[Hofahome]

Definitely sounds like vacuum leak. I think coolant temp sensor would be less likely. Welcome to the erratic idle club! Let us know any updates.

[Hofahome]

Oh and make sure you have the lines correctly installed without tears.

[sheldon0]

Did you maybe not get the crank case breather pipe lined back up under the supercharger?

That is somewhat possible and I've thought about it a few times. When I lifted off the SC I was wondering why it looked so "naked". Is there any change this piece could be missing but still worked before this change by luck? From pictures it appears there should be a plastic pipe few inches long that would sit on top of the engine on which I have to insert the SC, correct? I have pulled off the SC twice now and all I see is a hole with a little nipple around the ring but not plastic pipe or anything (not on the SC side either).

[SwankP3RF3ct10n]

You have a vacuum leak AFTER the throttle body. There is a small cylindrical pipe about 2 inches long that goes from the PCV system to the bottom of the supercharger (into the actual rotor housing itself). If you are missing that for some reason or the seal for it, you'll have issues. But whatever you've got, theres a vacuum leak problem somewhere after the TB. The ECU can't get a proper measurement of the air incoming in based on vacuum levels and tries to hunt the idle.

[sheldon0]

Thanks guys. Now I have to find out where this pipe went because I haven't seen it since I took this thing apart the first time. Does anyone have the part number for that pipe?

[SwankP3RF3ct10n]

#29 in the parts diagram in this thread. http://www.audizine.com/forum/showth...-photos-tips!?

[sheldon0]

I've used and followed that thread to do this job :) - but unfortunately it doesn't reference a part number :(


Edit:

NVM - after searching through my front yard where I sat the SC down my wife found the piece! Awesome news - Thanks again for the help figuring this one out. I'll be home shortly removing that SC for the third time and hopefully it will fix all my issues (I don't see why not).

[SwankP3RF3ct10n]

You're gonna need to dig that up on the Audi Genuine Parts website when it comes back up. Come on man... do some work. :p

BTW, it's kinda hard to "just lose" that part. It either fell off close to where you set the supercharger down or somewhere within your engine bay. It doesn't just disappear since it's not that small. I'd check to make sure that's what's missing or if it's something else, but look around in your work area like I said.

[s4osfan]

the s4 thermostat replacement guide I have lists the part as 06e 130 213. From the ecs website this looks like it, but it only lists this peice on the Q5 3.0tfsi, although I doubt it would only fit that model and not ours... Looks like there is an 'A' and 'B' version as well that do not look like they are the correct part, you want the one without the suffix.

https://www.ecstuning.com/Search/Sit..._213/ES280572/

[sheldon0]

SwankP3RF3ct10n:
I appreciate your help. I did try to search for that part on some of the audi websites but couldn't locate it, I figured I'll ask in case someone ran across it and had the part handy. Anyhow now that I found that piece (was hiding under wood chips) I'm a happy camper.


Edit:
s4osfan:
Thanks for that link. I'm sure someone might run across this and need that part number.


Final EDIT:
Thanks for everybody who added to this thread. It really helped me narrow down the issue. I'm glad it was something as stupid as a missing pipe. Car is running great again!