73 911 distributor idle issue

[crh]

Hi
I have a 0231 184 001 distributor on a 2.4S engine. I'm running a crane optical pickup (no points).
Issue i am having is strange idle response when vac disconnected

With vac connected, timing is stable, idle is stable
With vac disconnected, timing advances significantly past TDC, and idle races. Reconnect vacuume, and both return to normal.

Prior to this, I had distributor out and applied some grease to points base plate. I verified that sucking on vac canister freely moved plate and it returned to normal.

Engine temps may be running a bit hotter than normal (210 with ambient ~85), If memory is correct I normally would be 190-200.

Puzzled.

[edmayo]

Sounds like it is acting normal. Vacuum will retard from 5 deg. advance to 5 deg. retard

[crh]

Hi Ed

I could have been clearer, yes directionally the behaviour is correct, when I disconnected vacuume timing moved more than 10degrees I thought - I'll double check tomorrow.
Hope to see you in Kerville soon

Charles

[Frankr]

Long term high idle problem. My engine for this issue is a 2.7 RS clone 8.50/1.0 with some head work and GE 40 cams. Ran lots of track days etc but now it is out to pasture as a weekend cruiser. It has the Electromotive crankfire single plug system. The idle was always in the 1800-2100 range and would not adjust below that. MFI system was all new rebuild as was engine. Pulled 215 HP at the wheels. Over 30 years later it still runs exactly the same and uses maybe 1 qt oil every 1000 miles. But around town the high idle is a PITA. Hard to get into 1st/reverse and noisy. As I can easily change the timing with the crankfire what would be a safe baseline set of numbers. I dont need max performance. Current setting are about +8 degrees base. +25 at 3000 rpm and -3 at 8000. I use midgrade 91 octane Shell with none of that smog stuff in it. Rural VA.

[frederik]

Most likely your throttle bodies are worn so the air leaks around them. I assume you verified that the throttles are all coming back to fully closed when idling. Adjusting the timing won't help with this.