Re: idle speed regulator

["content22207" <brobertson@xxxx>]

CIS (Constant Idle Speed) system has been covered before (this is a
very good engine to search the archives):
http://www.dmcnews.com/search.html

But in a nutshell:

The idle speed motor serves the same purpose as variably cracking open
the throttle plates. This allows the engine to maintain a constant
idle speed through different conditions and loads.

There are actually five ways a PRV can breathe at idle:
1) Intact and properly functioning CIS system
2) Idle speed motor unplugged at an open valve position
3) Manual bypass circuit (brass screws in fuel mixture assembly)
4) Throttle plates cracked open with lower set screw
5) Vacuum leak(s)

You could have any or all of the above (except apparently #1). You
will simply have to diagnose.

My experience was a cantankerous CIS system: sometimes the idle speed
motor motor would stick wide open, other times it would stick fully
closed. I opted to remove the entire system from the vehicle --
including the ECU -- and idle with the manual bypass circuit instead,
which is how PRV's idled throughout the 1970's, before CIS was
developed as "bolt-on" addition. I also added an auxilliary air valve
for fast idle during engine warm up (pre-CIS PRV's had an auxilliary
air valve located in the same place as the idle speed motor, but I
re-located mine to the driver's pontoon for better access to the
ignition distributor and spark plug #4). Note that my PRV is NOT
factory original and is missing several sensors and switches from the
original CIS design (my idle speed motor was hard wired continuously
active).

If you ever want to try the same, please note that each brass screw
serves a different function. There is a specific procedure to set them:
http://f5.grp.yahoofs.com/v1/kF4NQDgizdFF_GPGNCdooBMUIEMGgEADFkR43GWPi63sKuzYYLJ3DBDu3xTL6LGsO7m2GTOO8yd7mCcEF69194y6v0hKzxWY350/Idle.txt

(That's a VERY long URL -- if it doesn't click OK just eMail me off
List and I'll send you a copy).

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "dmc12hank" <henrik@xxxx> wrote:
> Hi everybody!
> I have had my car for 3 years now, I realized this summer that the 
> idle speed regulator is disconnected. 
> Is this bad?