Car sometimes won't get off warm-up idle

[jzdude]

88 DX Carb Auto.

I try to gas the car to get it off the high warm-up idle but sometimes it won't get off it. Sometimes when I drive for 30+ minutes and then shut off the car and leave it off for less than an hour (even on warm days) the high warm-up idle comes back on.

Any ideas whats wrong?

[2oodoor]

More than a couple of things could cause this. This sounds Most likely the fast idle diaphram and or thermowax valve the controls that.
Fyi kicking it off fast idle doesn't work because on thes the choke opener system and choke fast idle are totally separate (which is crazy)

[g.frost]

* Refer to manual you downloaded here.
* Warm up the engine.
* Remove air cleaner to access carb.
* unplug Vac line 18 from end of choke opener. cap this port on choke opener.
* hook line 18 to your vacuum pump. (if you don't have a vac pump, get a mityvac or some such.
* start the engine. Note if idle speed is too fast.
* pump line 18 to vac and note if idle drops.
* If idle drops to normal on pumping vac on line 18, the problem is likely a vac leak in the choke opener.
* If idle does not drop, hook 18 back to the choke opener and proceed to test the fast idle unloader (using vac pump) per the manual.
* The fast idle unloader test will determine if it is the problem, a vac leak elsewhere in this circuit, or thermovalve A is failing.

[A20A1]

Also make sure you have coolant at the proper level and that you bleed it if necessary.