Very fast idle on warmup

Hello,
I helped a friend replace his clutch yesterday in his Civic. The reason it went out was because he has to use the clutch and brakes to slow the engine down while it is warming up. It idles at 4-5K when warming up even in the summer, he said! After 5-10 minutes, it runs perfectly. After it cools down for an hour or so, same thing.

It is an '87 1500 with the carburetor. Could it be the choke? How would I trouble shoot that? It was so late when we finished the clutch that we didn't have much time to look at it. I would like to disconnect the choke to see what happens, but I'm not sure how. The diagram in the Haynes manual shows the choke, but I think his car had an electric module(?) in that location (and so many vacuum lines, yikes). I shouldn't expect a vacuum leak if it idles normally when warm, should I?

Thanks...

1987 CRX/DX 1.5L Carb.: Try adjusting the Fast Idle Screw (should be in the Haynes manual). Looking at the engine from the front, it's at the left rear lower of carb, opposite side of idle adjust screw, kind of tough to get at, I came at it from the driver's side using a mirror on a stick to see it. It's a screw with yellow paint on it, turn it CC to decrease fast (cold) idle. Good luck.