Erratic Boost-'86 930

[orph]

Sometimes the boost does not come up where it should, but then on occasion it does. Wrench put a test gauge into the line, drove it , and seems to be short 9-10 pounds. But then again, on occasion, it will come up to full boost. His thought is an air leak, possibly worn seal on the pop-off valve, for he could accasionally hear it banging. Does this sound like a reasonable point to start looking ? On a 930, where in the world is the valve located ?

[RarlyL8]

The location of the pop off valve depends on the year of the car. I think (you'll have to look) on your car it is located on the upper left side of the engine, under and slightly to the rear of the intercooler, in one of the large intake hoses.
Hopefully someone more knowledgable with '86 models will chime in with a picture.

What size spring is in your waste gate? Losing 10 lb is more than the stock spring would allow to build.

[orph]

Thanks for the reply ! The car is a 1986 930, and the PO indicated it had a 1.0 spring.