Another possibility is that your carbs and/or return linkage is hanging up. Maybe try a heavy dose of carburetor cleaner on all the pivot points and "feel" if there is something getting stuck. You might check your return spring too and/or add a second return spring just to be sure the carbs pull shut when you take your foot off the gas.
Additionally, it could be that your carbs aren't tuned just right. What I mean by that is maybe the idle is set a little high to keep the car running when cold (choke not working exactly right) and once it warms up, that carb(s) setting makes it idle too high?
The idle solenoid will definitely open with the base grounded & a hot wire run to the spade connector. Hey, maybe your ground at the intake isn't all that good? If it's a '69 aluminum intake, maybe you could run an extra ground wire to the solenoid base? Just thinking outside the box here.
Another possibility I can think of is that sometimes people adjust the return linkage to leave the outboard carbs cracked slightly open to help the car idle. I tried this on my car and I got the same symptoms as you're reporting.....sometimes the outboards close all the way & it idles down while other times they stay open just a crack and it wouldn't idle down.
Last edited by PurpleBeeper; 05/10/16 12:29 PM.
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
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