I was leaving for JFK and walked to the old stop at Grand Central for the bus, only to find that the area has been pedestrianized, now has a bike rental rack and there was no sign of the bus.
Luckily I noticed that people were walking around the corner on East 41st Street, to the east of the Park Avenue Viaduct, on the South Side.
The new location is shown with the arrow below:
Why not take the E train to Jamaica and transfer to the Airtrain? The cost is 1 subway fare and the $5 Airtrain fee, and you aren’t stuck in a bus for an hour subject to traffic. Plus you can start anywhere in Manhattan on the subway and transfer to the E.