Microswitch question
 

I have an idle that drops down to zero and then comes back up and I believe this problem is related to the microswitch. Just how does the microscwitch function and how can I properly adjust it or test it to determine if indeed is the problem. In fact to sound even more frustrated, just what does the microswitch do? Is it cheap to replace?

Thanks
Bob

73.5 T

Bob, There is a microswitch on a 73.5T w/CIS (item 14 in the 73 wiring digrams here on Pelican) but it is switched to a contacts closed position when you pull the hand throttle lever all the way up. It's only function is to send power to the cold start valve while the starter is cranking and only while the starter is cranking. The switch is located on the throttle linkage on the driver's side of the throttle body. The hand throttle of course affects idle as it mechanically opens up the throttle valve. Under what circumstances does your idle speed drop to zero and return? Jim

Bob, It could be your deacceleration valve (vacuum limiter)is bad or leaking. Also could be bad hoses to this valve. It is item #7 in this figure:

http://www.pelicanparts.com/911/911...78-83/1-7-2.JPG

:D Jim

Jim...
I think I have had the CIS from hell, but its getting better.

Without going into great details about component replacements, constant adjustments ( I wear the 3 mm mixture adjuster around my neck now!) and other things I have done to finally get this baby to turn over (start) when cold, the idle problem plagues me the most. I definitely have to use the hand lever on start up and usually stay at 1800 - 2000 through warm up. If I let it down too early the idle will surge or get close to shutting down. I believe this is normal. After I register 140-180 degrees, I will lower and see if it dies coming to a full stop. I have been lucky and that has not happened, so again everything seems fine. Once warmed up, the great majority of the time I come to a stop thereafter, the idle goes to zero and thens bounces up directrly to idle setting at 950. No alternator light or sputtering. The other few times the idle will drop to 200 or 300 hundred and back to 950. I do not know where to go from here......The car runs incredibly fantastic once warmed up......aside from the idle issue.

Are their any other adjustment points? Thats where I thought the microswitch can come into play.

Thanks

Bob

Read this thread about adjusting decel valve:
http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=52642

The surging idle still sounds like a WUR problem but you said you replaced that already.

Jim