It leaks in a strange place

[ncoder]

I have a high idle on my 930 when warm, so i did some diagnostics.

Found a leak around the bolt of the throttle valve.



I'm not sure how to fix this. Tips?

Boroscope + Smoke test video:
https://youtu.be/jUvPxzPFSCQ

[FirstDotLast]

Looks like the throttle shaft seal/bearing is leaking. The seals aren’t available and I believe there’s no rebuild kit (someone correct me if they know of one). The two options are rebuild the throttle body yourself by replacing the needle bearings and using proper orings in place of seal replacements or buying a replacement throttle body which can be a crapshoot if buying a used one.
See here: https://www.instagram.com/p/DBwgfGxS8vK/

Side note… how did you do this smoke test on your 930? Where did you apply the smoke on the engine and did you close off the air meter/intake?

[ncoder]

Thanks for the quick reply! Unfortunate it's a bit of bad news. I looked at your post. Did you have to machine anything, or just find the right size O-rings? I havn't looked at my throttle assembly yet, so I don't yet have a mental picture. (unclear from your posted picks what is the before vs after)


You'll find this funny, but it turns out a standard kitchen sink stopper is just the right size to block the intake above the throttle valve



I then piped the smoke machine through the Auxiliary Air Regulator, since I knew it was open while cold and leads to the right place.

I didn't have the proper baloon-looking thing to do it the normal way.

[ncoder]

Found a useful post: https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/1136383-930-throttle-body-rebuild.html

[gorskined]

did you check your aar valve for an internal leak? . simply run up to temp so it has the elevated idle. Then shut off car remove the hose from aar and plug it. Re start to see if your idle is still elevated . why cant you just adjust you idle when warm to compensate for the minimal air leak. you can also try using a sprayable grease goes on like water then evaporates into grease. spray it a few times while running it will dry up and eventually thicken up closing the gap a little.

[ncoder]

I did check the AAR valve. However I just plugged it while cold, ran the car with the ARR plugged and just compared the idle speed once it got hot. It was high enough that I wasn't looking for a small change. That didn't seem to affect anything, so the AAR valve seems okay.

I've adjusted the idle in the meantime, as you suggested. Boy, that adjustment procedure! I got clever and used a borescope mounted on my screwdriver. Can't imagine getting this done without one! How do you guys do it?



https://youtu.be/dIRuylpplvw

Related, i found someone local selling a used throttle body. The number is off by one, I'm hoping it's close enough.

i've found a 930-110-250-07
what i needed was a 930-110-250-0[8 or 9]

Once i get the part off i'll see just what's different (if anything)

This is after i test the "new" one to make sure it's also not leaking, of course.

[kevinkross77]

Nice catch on the throttle valve leak. A high idle when warm is often associated with air leaks in the intake system, and this seems like it could be the culprit.

If you’re seeing a leak around the throttle valve bolt, it could be that the seal or the bolt isn't tight enough, or there’s damage to the throttle body or surrounding gaskets. Here’s a step-by-step approach to address this:
Steps to Fix the Leak:

Inspect the Throttle Valve and Throttle Body:
Remove the throttle body (if necessary) and inspect both the valve and the body for any cracks or wear. If the throttle body has been subjected to high heat or age, the gasket surfaces can sometimes warp or crack.
Check the condition of the throttle valve itself. If it’s worn or damaged, it may need to be replaced or resurfaced.

Replace or Tighten the Throttle Valve Bolt:
If you’re confident the leak is around the throttle valve bolt, first ensure the bolt is tight, but not overtightened, which could damage the threads or warp any surrounding components.
If the bolt or threads are stripped, you may need to use a helicoil kit or re-tap the threads to restore proper clamping force.

Check and Replace Gaskets:
The throttle body gasket may also be compromised. If it's old or damaged, replace it with a new one. These gaskets are relatively cheap, and they can make a big difference in fixing vacuum leaks and regulating air intake properly.
It’s a good idea to clean the mating surfaces of the throttle body and intake manifold before installing the new gasket to ensure a proper seal.

Smoke Test Check:
Since you’ve already done a smoke test, it’s good to have ruled out other common sources of vacuum leaks (like the intake hoses or any other components). If you still see smoke around the throttle valve area after tightening everything down and replacing gaskets, you may want to consider the possibility of a worn throttle shaft seal, which would require a rebuild of the throttle body.

Recheck Idle After Repairs:
Once everything is tightened and sealed, start the car and see if the idle stabilizes. Check for any signs of unsteady idle, misfires, or other erratic behavior. If the issue persists, you may want to look into the idle air control valve (IACV), which can also cause high idle when faulty or stuck.

Additional Tip:

If the car's idle is still fluctuating or high after addressing the throttle valve, you might want to verify the AFM (air flow meter) and check if it's calibrated correctly. Sometimes, a vacuum leak can throw off the AFM readings and cause an idle issue.