I've just bought a 1990 Honda Civic DX with an AT. Lately I've had a hesitation/stalling problem...mainly at stop signs and when merging into traffic as I accelerate. It seems to happen when the car is warm. Seems like if I shift from D4 to D3, the car recovers. If it stalls, sometimes it will start right away, other times it needs a good 10 minutes...that's a problem when you're merging into traffic.

Replaced the fuel filter, changed some temp fuel sensor, checked the fuel pressure, had it in the shop for 8 hours. No codes, no ideas from the shop.

Anyone have thoughts?