The throttle body on my 04' s60 turbo was a bit dirty so I decided to clean it. The engine ran great but these TB's are known to gunk up and cause unstable idle condition.
See before and after pictures below.
Problems after putting things back together:
Car ran rough, backfired, uneven idle, flashing check engine (no codes), running rich and black soot deposits from exhaust.
The reason I'm writing this post is because all of these symptoms were due to an air leak.(reused old gasket)
After inspecting coils, plugs, air hoses I was able to find the problem by spraying carburetor cleaner in the areas between TB and intake. When the fluids was sucked in, the engine ran smooth.

Anyone doing this job is advised to replace the gasket which is <$5.00

Cheers

 

You may need to clean your pcv system. When the pcv system gets clogged up you start to get oil into the intake system and it builds up on the throttle body. When the throttle body is closed there needs to be air going under the blade. So without cleaning the pcv system it will happen again.

 

Cleaning the pcv is on my to do list but I'm still searching for the most efficient way to tackle it. Thank you