Article by: Igor Kostenuk
Article applies to: all BMW models with the S38 Motorsport engine.
I decided to pull this job on my M5 a couple days ago and document it as much as I could.
This job requires a couple of special tools which I will list and other things that need to be done prior to doing this job in order to do it correctly.
PRIOR to adjustment:
All 24 valves must be adjusted to spec (0.28 to 0.33mm)
All ignition components in full working order ( Cap and rotor, coil, spark plugs, wires and crank position sensor)
All vacuum lines under the Intake Plenum must be fresh, can’t have vacuum leaks.
All vacuum related rubber o-rings must be replaced.
Tools Needed
Carbtune tool http://www.carbtune.com/
Vernier Calliper
Feeler gauges
10mm socket
8mm socket
7mm socket
Screw drivers
Parts needed
Brass screw o-rings 17211742635 x6
Throttle body to plenum o-rings 11611305124 x6
Vacuum hose, 1-2 meters of it.
Procedure
Remove the intake plenum and replace every vacuum line in your sight:
Remove the TB shocks using an 8mm socket or wrench:
This is what they look like:
Adjust the shock according to BMW specs:
Use a vernier calliper to adjust to 98mm:
Clean up the little shocks, use a drill with a wire brush bit, treat with oil after cleaning them.
Next step is to adjust the ITB throttle valves:
Adjust by BMW spec (top 21.7mm, bottom 22.7mm)
Assemble everything back, use new o-rings between the ITBs and and Intake plenum tubing (sorry forgot to take pics of that)
O-rings p/n#: 11611305124. Assemble all the ITB components back.
Now start removing the brass screws, use 7mm socket:
Remove all of them, be careful, if they haven’t been out of the in a while, you can strip or break one, they are made from brass, very soft material.
This is what they look like out:
Clean out the holes as much as you can:
I used a pick and 600 grit sand paper:
Remove old o-rings:
Clean up the brass screws using a drill and a wire brush bit.
New O-rings:
Install new o-rings:
Screw them back into the ITB’s:
Tighten to the end and do ONE full turn back (360 degrees):
Now I’m going to replace the spark plugs and the ignition coil (mine were due).
After this I will start balancing the ITB’s.
NEW coil:
New spark plugs:
Old vs. New:
Set spark plug gap:
Now the Balancing begins:
Connect carbtune vacuum lines to the ITB ports, you can only do 4 ITB’s at a time with this tool, so leave the other two plugs in on cylinder 5 and 6.
After, just move two vacuum lines to cylinders 5 and 6 and plug cyl 1 and 2. Use cylinder 3 and 4 for reference.
Make sure the tool stands vertically.
ENGINE MUST BE AT OPERATING TEMPERATURE, YOU CANNOT DO THIS ON A COLD ENGINE
Start the engine and observe your carbtune. Use a 7mm socket to adjust. Tighten in increase vacuum, loosen to decrease vacuum.
BMW says they should all be around 22.7 in Hg. I wouldn’t worry about that too much, make sure the readings are more less on the same line and the idle is from 850-950rpm.
This is how it works, the higher your vacuum is, the lower your idle speed will be, the lower your vacuum is, the higher the idle speed will be.
And DONE.
Bonus pic 
