All of you supercharged owners might be interested in the following:

While troubleshooting and trying to find the cause of a rough idle on my supercharged '92 SSE, I tested for vacuum leaks by spraying injector cleaner around the base of the supercharger, and although no idle change was observed when I sprayed it at the base gasket on the pulley side of the supercharger, where it is reportedly prone to vacuum leaks, or while I sprayed it around the rest of the base gasket, a BIG change was observed when I sprayed it around the butterfly valve shaft attached to the boost bypass valve - the engine stumbled and almost stalled so I stopped spraying there.

I first thought I had found a vacuum leak, but just for kicks I sprayed it on the same area of my '93 SSEi which has a smooth idle, and the engine stumbled on the '93 also.

Conclusion: It seems this area of the supercharger normally leaks air. Have any of you ever tried this?

So my hunt for the cause of the rough idle continues...

Bill, the vacuum fitting under the nose of the SC is only on the M90 (Series 2).

I currently have my SC torn down, and I can tell you the bypass shaft is not airtight. I think that'* normal.

[quote="willwren"]Bill, the vacuum fitting under the nose of the SC is only on the M90 (Series 2).

Bill, I wasn't referring to the vacuum fitting under the nose of the SC; I was referring to the base gasket on that side of the supercharger; I've read that this area of the gasket on the M62 is prone to vacuum leaks. At this point, I almost wish I had found a vacuum leak around the base gasket - at least that'd give me a clue to the cause of the rough idle. It'* no fun sitting in traffic in a car that has a rough idle.

My motivation for writing this post is to let others know that it seems normal for the shaft for the butterfly valve to leak air.

A mechanic once tried to convince me that there shouldn't be a leak there (he showed me by spraying WD-40). I couldn't think that there was anything abnormal (I must admit that I did try to stuff an O-ring in there).

I am having some idle issues of my own recently. Haven't been able to figured out what'* causing the issue, either.