911 Turbo "Hunting" at idle
 

I have a question that has given me on and off problems for a few years. I have a 1978 930 Turbo, with 964 cams, set at .54 Max advance, a K27 Turbo, and an aftermarket muffler. I set my timing slightly advanced then the normal 10 ATDC the book requires, its around 0 now, vacum retards the timing at idle to about 5-6 ATDC, with a mixture of 2 on CO, it hunts after warming up a little about 500 RPMs, We can find no leaks anywhere, as the engine was rebuilt in my shop a few years back, I have checked and checked everything I can think of, if I set the timing at 10 ATDC, it wont hunt anymore, I have tried 2, 2.5, 3 on CO, it only seems to move the hunting to a warmer stage.

Question I have is the timing finally make it hunt combined with the 964 cams? Is there nothing I can do? I dont want to retard the timing again, as its WAY to sluggish off idle, and runs better with it where it is, I have an ANDIAL 7th injector for enrichment. It seems, I might have to live with the hunt, in order to kick in more timing, and no, i do not have a pre-det problem.

Thanks

Since noone has responded yet, I'll give it a try, although my experience is limited to non turbo cars. Do you have a WUR? Have you checked your control pressures? Maybe they are just a little bit off for the particular heat range you are in while warming up.

I'll second that and add that I can create a "idle hunt" by moving my throttle bypass screw up a few hundered RPM's, thus creating a mixture change, so the WUR control pressure should always be suspect when this happening.

I hate to ask, but what are you refering to with WUR?

Thanks