no fast idle when cold

1993 Toy 2wd 22re 5sp 210,000 mi.
Suddenly I have no fast idle when cold. Any ideas what to look for?
I'd like to know how the fast idle system works. I assume there is a
heat operated vacuum valve that opens a diaphragm to let more air into the manifold. Is that correct?
Q
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wrote:

it starts but no fast idle? i confess i don't know how the system works but i think there's a cold start injector to richen things up and the rest of the system ups the idle speed to compensate for the extra fuel.
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Jeb,
Yes, my understanding is that there is a cold start injector, which appears to be working. I tested it by unplugging the cold start thermal switch which made it very difficult or impossible to start when cold. Plugging it back in made it start fine but I have to keep my foot on the throttle to keep it running fast enough so it doesn't die. Once warmed up for a couple minutes, the idle is fine. The problem appears to be with whatever device is supposed to let more air into the manifold.
Looking under the manifold I see a diaphragm with a vacuum hose going to it (not the EGRV). I think that may be what is supposed to let in extra air. Anyway I've ordered a shop manual which I assume will have the diagnostic procedures.
Q
JeB wrote:

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Do you have Fuel injection or carburetor ? If it's carburetor it works off a choke. The choke regulates the position of the butterfly in the carb.Check on the web on how to regulate.Good Luck.
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It's a 93 which is fuel injected. If it had a carb, I would know how to fix it.
Q
W.T. MC GLYNN wrote:

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Some useful information: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml#ThrottlePositionSensor
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Thanks Keyser,
I've tested and adjusted the TPS and it's working fine. The TPS doesn't controll the fast idle when cold.
Q
Keyser Soze wrote:

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Well here's another link: http://autorepair.about.com/library/faqs/bl524g.htm
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Hi Q I am not familiar with your model, there will be an idle compensation valve fitted to the inlet manifold this is the first place to check they usually carbon up but can be genuanly faulty. Joe

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Thanks Joe,
You're right. I just fixed it yesterday. The device is basically a thermostat that is heated with coolant from the engine. It opens an air passage in the throttle valve assembly, letting air past the butterfly valve. When I cleaned out the throttle assembly the other day I tightened the locking ring in place, not realizing it is for adjusting the valve. I removed the assembly, put it in a pot of hot water on the stove and observed it's operation. After adjusting it, all is well.
Q
Joe wrote:

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