[DML] High Idle Issue

["Mike Polzin" <MPolzin@xxxxxxx>]

Greetings everyone,

It spring so I am back to working on my cars again. I have an '81 5-speed that has a high idle condition. Last fall I suspected that the idle speed motor on the car was faulty because when I banged on it a bit the idle on the car would go down for a little bit. The car was in generally idling around 2000+ RPM's when warm, and sometimes upwards of 2500 RPM's if I was driving around for a bit.

Well I replaced the idle speed motor (thanks Toby!) and the car is still idling high, however it now seems to max out around 1700 RPM's warm, so there is an improvement and I think the idle speed motor was part of the problem. I backed of the idle screw on the throttle but I can't go any further down at this point, so it isn't an adjustment.

What I noticed was that when I pushed in the clutch I could hear a slight "woosh" sound and the motor would idle down to about 1500 RPM's by simply doing this. I did not put the car into gear.

Also when I turned on the heating/cooling fans inside the car the car would idle up about 100 RPM's. 

I pulled off the hose that goes from the oil fill to the air filter, which made no different in the idle, however when I blocked the hole on the oil fill cover the idle dropped by about 200 RPM's.  

All of this leads me to think I have a vaccuum leak somewhere causing the high idle. I have looked for it by spraying some carb fluid around some of the common leaks around the intake, but couldn't find a leak there. I know there are other places to look, can anyone advise? Or is there anyone in the Wisconsin or northern Illinois area that would be willing to assist me in locating this? Thanks much!

Mike Polzin






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