[SpadedOne]

Originally Posted by storm66

Ok so I pulled the front end off the engine, changed the crank pulley and checked the timing belt to see if it had jumped a tooth. Cams were spot on. Cranked the engine vibration still there at around 1500 and 5500. Ugh!!!! I am going to push this thing off a cliff...

But wait I started reading and although I see no one describing the problem as a vibration I did note that the engine has always seemed to have less power that my other SVX which is an automatic. So let's put two and two together, a vibration at two points only through the RPM range and lack of power. The Iris valve apparently transitions or changes open/closed state at 2000ish and 4000ish RPM and if it is not functioning can cause lack of power. So I pulled the power steering resevoir again and got to the iris control vacuum check valve and did the (blow/suck) test (ok no jokes please this has been painful enough) and it is not functioning properly (does not check). So I went to Advanced auto and got an off the shelf $5 vacuum check valve and replaced it.

Problem solved, No vibration and it runs like a bat out of the really hot place.

So take it from me, check the check valve first....

I've only drove 2 SVX's. Mine and another one. The other one seemed to have more power than mine. I have a power steering leak. It's the O-ring. I'm going to be replacing it on Monday. I would like to check my Iris valve to see if this is my problem with the power, but have no idea what or where it is. Can some please elaborate on what it is and how to change it? Any pics? Part number from Advanced?