Engin runs roughly after warmup

[fordmerc]

Car idles roughly after 3-4 minutes. It is fine per timing light and vacuum measurement initially, but as soon as it has run for a few minutes it becomes rough. On the street at 25 mph it seemed OK, but almost stalls at stop. Any suggestions?

 

[Owen_Dyneto]

You don't give a lot of info to go on.  What year and model Packard would be somewhat helpful.   I'd start with a good comprehensive tune-up, plugs, high tension wires, cap, rotor, points, condenser.  If your coil feed wire is in an armoured conduit, replace it.  Then check fuel pump pressure and volume of delivery.  Clean fuel filters, check carburetor float, needle and seat, and fuel level.  If the carb vent clear or if a later model, are the anti-percolator valves functioning?  After you've been thru this, if the problem still persists, then come on back and let us know.

[fordmerc]

Sorry about the info deficit: car is the '41 120. All of the checks above have been done except the carb, which is a relatively recent rebuild (professional). In that vein, when the engine gets warm and rough, the choke is fully open as expected. However,closing the choke or covering the intake makes the engine run better again! I suppose this makes it a carb issue, so, I can try to tear into it or send it back, but any comments might make it easy for me to solve the problem myself. Thanks.

[Owen_Dyneto]

Since it improved when you provide some choke, that would lead to the conclusion that you have a vacuum leak.

[fordmerc]

Problem resolved!! I readjusted the idle mixture adjusting screws since I didn't identify any vacuum  leak.  I suspect there was something in the jets that was dislodged by my fiddling. I learn  something every day.