Cold weather starting trouble. Need help.

[doodah man]

This morning went out to start the truck in ~27* temps. It starts right away but the idle is really rough. I made a video on my phone and I'll post it in this thread if I can figure out the YouTubes.

So it idled rough and slow for about 5 minutes. I gave it gas every now and then, but it didn't feel like it was going to die. When the needle on the temperature gauge got to the first line, it smoothed out but was more like a fast idle; pretty high rpms. I blipped the throttle but the rpms would not slow down. I put it in drive. Still high rpms. Then I just drove it. It would get up to about 15 mph without even pressing the gas and I had to really get on the brake to stop it. Once I got it down the road a ways and it was fully warmed up, the idle was back down to normal, and I drove it 80 miles home.

The fast idle worked the way it's supposed to, until this summer. I noticed sometime this summer that it wouldn't drop out of fast idle when I blipped the throttle, but the rpm would usually drop when I put it in gear.

Is this the choke sticking or not working properly? It's a Rochester Qjet. Based on the casting numbers (7045213) it's a 1975 for a manual trans. I've got an automatic.

I sprayed it down on the inside with carb cleaner when I got home, but won't know if that did any good until tomorrow morning. Any ideas what might be going on? Thanks in advance as always.

[doodah man]

Anybody got any ideas?
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[mrein3]

Is the choke the style that is operated by a bi-metalic strip under a tin heat shield? If so, after the truck warms but is stuck on high idle, carefully touch the raised area on the intake manifold under the choke thermostat.
If it is not hot, that passage may be clogged with carbon from the combustion process.
In a properly working, stock system, that passage heats up from exhaust gas and operates the choke through that bimetallic strip heating up. When that passage is blocked by 40 years of carbon build up the bimetallic strip won't heat up and work properly.
If this is the problem, the fix is to remove the intake and chip that crud out of there.
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[Aaron Burkemper]

You may also want to check the choke pull off. That may sometimes cause a rough initial cold idle until the choke opens a little bit.