What setting should the choke be at for colder starts (due to the colder weather coming)

I ask because during the summer and up to about 3 weeks ago, the car would start up and run a tad rough for about 30 seconds and then idle smoothly

For about the past three weeks, I start her up and she idles VERY rough (I have to rev it for about 5 minutes before it finally can idle decently without hesitation)

Im GUESSING its the choke --- however I could be wrong.
ALSO, if I open the top butterfly all the way (choke butterfly) so the maximum amont of air is sucked in, she idles smoothly as opposed to when the butterfly is 3/4 closed.

Soooooo is the choke the problem???? Would keeping the choke constantly open cause a problem???
Note: I just purchased a hi-flow Edelbrock filter (the triangle shaped one ) that will allow for better airflow than the stock one woooooohooooooooo!

haha, again, the car ran and idled fine during the wamer weather and the choke was set for the warmer weather when it was installed back in June (guy up the street who helped me with some tuning issues set it)

thanks ahve a good one

If you set the choke to stay open, your engine won't start when it's cold. That's why they have chokes in the first place.

The choke setting doesn't vary from season to season, once you get it right it will be right all year. The adjustment on the choke thermostat is there just to compensate for when the choke spring ages and loses it's strength.

What it should do is the choke plate should snap shut firmly when the engine is cold and you depress the throttle to the floor. That also sets your fast idle cam so the engine idles a little quicker while it warms up. As the engine runs, the choke thermostat should open the choke fairly quick, with 3-4 minutes or so, then the choke plate should be straight up.

To set up the choke, start with the marks straight up, and if the choke plate snaps shut firmly, you're there. If it's weak, you can move to 1 rich, 2 rich, 3 rich, etc, but remember the richer you set it, the longer the choke will work, wasting gas.

After you get the choke plate where you want it, check the operation of the fast idle. I never used to set them at factory spec, because I always liked my fast set at 1000 or so, just fast enought to keep it running smooth but not overrev it while it's cold. That is set with a screw on the fast idle cam behind the choke thermostat. You can set this with the engine warm by just moving the fast idle cam into position with your finger.

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

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