Jetdriver69

On my 82 5 speed with 700 mile rebuild engine, when I set the idle cold at 850 rpms the car runs fine, but when warm the idle increases to about 1050 or so. If I turn it down warm to about 900 rpms warm the cold idle settles to about 700-750 rpms.

Could this be indicative of a small vacuum leak or is it normal for a slightly low cold and slightly high warm idle rpm? BTW, I have a new O2 sensor which cured a surging idle when warm I had right after rebuild. Thanks!

z driver 88t

Sounds like the cold start valve may not be functioning properly. I had to trouble shoot mine a few years ago, located on passenger side near rear of engine. Its been a few years so I don't recall the exact procedure. There is an electrical connection and a vacuum line connection. Make sure the vacuum line is connected and electrical connection is good.

Also as I recall the cylinder head temp sensor (CHTS) helps control fuel mixture as well and is a common fault point. Faulty CHTS could be running not rich enough at startup. All of this is a bit foggy; it was one of my first 928 trouble shooting projects.