Fast idle only when warmed up

[lowmileage]

I don't have a fast idle when starting the car and it is cold. When the car warms up, I get a fast idle that won't go away. What gives

[RABarrett]

The most obvious likelihood is that the choke coil is connected backwards, causing the choke to close when warm, not cold. It is also possible for the idle to be set fast, and the choke being inoperative, causing the choke not to close at all. Then the engine does not run until warm, when the fast idle causes excessive idling speeds. First check the operation of the choke, and fast idle linkage. If it works, you have eliminated one of the many possibilities. Ray

[lowmileage]

Hi Ray,
The choke is Ok because it does shut when cold but opens when hot. I rebuilt the carb - even though I took a bunch of digital photo's, I had "issues" about getting it back together (the linkages) but think I got it right now - but something is still wrong. The choke only opens half way, even when hot. It appears the secondary pull off bracket prevents the linkage from moving all the way but I didn't disconnect that particular linkage when I took the carb apart & the secondary pull-off can only go on one way? Also, when warm, the fast idle cam adjusting screw still contacts the fast idle cam. I'm not sure if that is correct or if the cam shouldn't contact the adjusting screw after warm up. What really gets me is why the choke "butterfly" doesn't open up 100% when warm? Before carb rebuild, the vehicle just about "ticked" over on idle. I'm wondering if the Gunk and water hose used on the motor compartment just recently has caused some sort of screw-up on sensors (even though '85 is primitive compared to newer models) ?

[lowmileage]

After looking again at all the linkages over the weekend, I've come to the conclusion that my problem is a combined problem with the fast idle cam adjusting screw and the choke. I think I had the choke tension too tight (I've backed it off some) and the fast idle screw turned in too much. I'll have to get the right combo.