I have a Automatic Accord 1991 i think it is a EX
when I drive it (through the city) it downshifts for no reason. Can anyone point me in the right direction. To start troubleshooting this problem.

 

The first thing is "Changed the fluid and put in Honda Z-1 atf?"
Secondly trans pressure lever cable adjusment?
From the throttle body there is a cable going to the pressure lever on the front side of the trans.
If some mental midget tightened up the throttle cable to boost up the idle speed it throws the synch out of whack.

With some slack in the throttle cable idle should be around 700 RPM, In gear foot on brake.

Driving test.... Going along a level road light throttle at 25 mph and then flooring the gas, the trans Should go to first gear.
Repeat the drive at 28 mph floor the gas pedaland it Should only go to second gear.

Pressure lever cable adjustment.....with the cable backed off to having slack, tighten so that the pressure lever on the trans JUST BARELY moves upas the engine rpm increases when opening the throttle

I usually put a long screwdriver on the end of the pressure lever and hold it with one hand while turning the throttle open with the other hand, helps to detect the slight movement of the pressure lever.

 

Someone said some type of module under/on the floor board may have moisture inside it. Does that sound right?