4000s, 4cyl, rough idle on restart

[S. Jaworski]

My sold 85 4000s is haunting me. The new owner said it has a problem on
restart. Something to do with cold weather, it worked ok when it was warmer.

Its a 4 cyl, non quattro car.
These are the symptoms:
1. Starts ok, runs ok . . go to store . .shut off engine.
2. Come back to car in 15 minutes . . it starts up . . idles rough . . bogs
down when gas pedal stepped on . . no power.
3. 30 seconds later . . it all clears up and engine runs fine.

I cleaned out the isv valve before I sold the car, cleaned the contacts, put
stabilant on them. Car has new plugs, new wires, new cap, used dist from
Shokan(old dist had bad hall effect sensor).

Anyone got any hints for me?

Thanks
Sylvester