View Single Post
mark houghton mark houghton is offline
Registered User
mark houghton's Avatar
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,860
Originally Posted by fredmeister View Post
If you are running the warm CP at the low end of the spec then it will tend to be rich on cruise. You might then be running the idle adjustment screw at the full lean end of its travel to get idle back to a lean enuff range. Basically one control set at the minimum and the other set at max leaves you no wiggle room of adjustment left.
Maybe try increasing warm CP and then richening up the idle control screw to get back to 12.5 to 1 idle and see where the cruise is then.

I dont know much how that freq control valve effects things as i have no esperience with it in my 79 930.

Good luck,
Good advice. FWIW, when the lambda system is in open loop (unplugged sensor) the frequency valve will default to a fixed duty cycle, if I recall it's 50% but would have to look it up in the book. So the freq valve then becomes a constant that you tune around.
The other unstated possibility is that the AFR gauge isn't properly calibrated and is reading richer than it really is, since the car seems to idle so much better at 12.5...which is really pretty rich for idle. But each car seems to have it's own sweet spot.
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 04-01-2013, 07:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)