Originally Posted by djenyc
For throttle plate shaft, it's not a simple o-ring, it's a composite pressed-in seal that looks kinda like a miniature crankshaft seal. It's very bad, as I can see a gap between this seal and the throttle plate shaft and I'm sure it's causing a vacuum leak, but don't know where to get a replacement.
Finally got the leak via the shaft verified. Got another replacement throttle body - tested good, put it on.... But my saga was not over.
That good throttle body fixed majority of the idle hesitation, but I noticed that the car still had a small amount of vacuum leak as RPMS would occasionally go up and down at idle. This weekend I took the manifold apart and went over everything with a fine comb - comes out one of the studs that secures the manifold was missing. WTF.
Apparently the missing stud was letting just a little bit of unmetered air in to one of the cylinders. No idea why it was missing, this things don't just unbolt themselves.
So I got a spare engine and just took the stud off that engine and bolted it in and put the manifold back and now it is all good yea! But it took me like the whole weekend to figure it out, so I'm also MAD.
Now both of my VXes idle good. And they run good too. So for future reference, if anybody is seeking for a solution to an idle problem - it's a VAACUUM leak. In my case of 2 cars and three engines, it was: MAP sensor O ring, Throttle Body Shaft Seal, Manifold Gasket - all vacuum leaks.
I'm still not sure of a good way to find them though. I tried pressurizing the manifold and it did not show the leaks. May be $800 be smoke machine would work. If you got an idea on how to find a vaacuum leak - post it please!!!! As I still don't have a good way of finding vaacuum leaks. It basically took me 2 years and many many weekends of swapping parts back and forth to figure mine out, doesn't seem right, must be an easier way.