83 911 sc distro question

[Reiver]

Guys/Gals..
I pulled the retard vacuum line off the distro and blocked it. I like the way it 'goes' in this fashion....revs remain higher between shifts allowing easier selection, seems to run cooler. Just 'smoother' overall.
The problem is at idle...wants to remain higher and very slowly seeks the proper 950 rpm if not coaxed if at all.
The advance vacuum line is still in place.
Do they operate in concert as a push/pull?
If both in place it idles properly....but one has to match gears a bit more precisely and it runs a tad hotter and I understand the retard vacuum was an emissions deal.
It is not a function of the airbox lever returning to idle location as this is functioning properly and hitting the stop immediately.
Does the advance vacuum work with the retard to set idle?
Does the vacuum advance work only at idle or thru the rpm range?
Thanks from a P newbie.

[Flat6pac]

The retard works at idle but im sure there is vacuum there through the range. The retard should be complete when the throttle is closed dragging you from 5 degrees BTDC to about 5 degrees ATDC. As soon as you come off idle you should loose most of the retard.
The advance tubing is above the throttle plate for vacuum and there is not enough vacuum created until higher RPM. Thats where you get the additional advance to get you near 30 degrees advance.
Bruce

[Reiver]

So the retard pulls the car down to idle? IOTW without the retard vacuum line in place it will not seek idle properly?

[Scott R]

Originally Posted by Reiver

So the retard pulls the car down to idle? IOTW without the retard vacuum line in place it will not seek idle properly?

You can disconnect it, just set the timing appropriately and the idle bypass setting.

[Reiver]

Scott,
thanks.
I did not reset my timing I just readjusted my idle rpm down to 950. Sorry, but what/how does one set the 'idle bypass setting'?
BTW, stock motor with cat bypass with co sensor in place.

[psalt]

Reiver,

You do not need to reset your timing after plugging the retard, timing is set with both hoses plugged at 5 BTDC at 900 rpm. Idle speed is set with the bypass, not the throttle stop screw. If this was touched, reset it by the manual. Usually plugging the retard will have no effect on returning to idle speed, usually the biggest effect is cold idle speed. The Decel valve is usually the culprit here because its purpose is to hold the speed up to lower emissions. Anything is possible if you have vacuum leaks or incorrect mixture. Make sure your hoses are not swapped, the retard has full vacuum at idle, the advance has little or none. My advice would be to set the timing correctly, set the idle speed to 900 with the by pass, check for vacuum leaks at the injectors and check the mixture by reading the duty cycle at the test port. If this is all correct, start reading up on the Decel valve, you can disconnect it or change its behaviour with a hammer or channel locks. Just like on TV.

[Reiver]

Paul,
Ok got it. I did not mess with the throttle stop, just mentioned it had full movement. I was adjusting with the bypass but didn't know what it was called lol.
Pretty sure I have no vacuum leaks, it's been well maintained b the PO and just had the 12k service 2 k ago.
I'll be reading up on the decel valve then...mucho gracias.

[Reiver]

Ok, am looking at the decel valve and small rubber hose...so just unplug the hose and plug both ends (valve end/hose end)?

[psalt]

Reiver,

Yes, see here (and others)

'83SC - Strange Decel Valve Behavior

[Reiver]

Good, thanks!