After blowing out the automatic transmission in my '86 Honda Civic Wagon the only cheap replacement I could find had the following weird quirk. It did not shift automatically through the gears. To change speeds I have to shift manually, without a clutch of course. In doing this it works fine. Any ideas what’s up?
I am not exactly sure when Honda went to an electronically shifted transmission. If this transmission still has a governor and throttle valve cable, I would look for a stuck governor spool valve or a leak that allows line pressure on the governor line. I am assuming that if you put the manual shifter in Drive the transmission starts in 4th and that you can get 1st, 2nd, and 3rd by selecting that gear manually.
If you can get the valve body out of the transmission, you might have that cleaned, inspected, and new gaskets installed.
This is an interesting situation. Let us know what you find and how you solve this problem.
Hopefully, transman 618 will reply.