i have a 91 accord lx automatic and when sometimes it has trouble with accelerating from first gear and on the dash the d4 light blinks. after it struggles on first and automatics shifts to second, it drives like normal. is the transmission bad? bad auto ecu? or some kind of sensor is bad? thanks....im posting this up for my dad, dont have any experience with auto accords, i drive a manual integra.

 

For the 91 Accord, usually a bad Transmission Control Unit (TCU). If it is the TCU, you can try to fix it yourself.

http://techauto.awardspace.com/transmission.html

 

Try shifting it manually. If the trans shifts fine manually from 1>2>3 then the problem is likely the transmission control unit as mentioned, which is a common failure on '90-91 Accords.