I have an automatic 1990 Honda Accord and the sport light flashes and has rough shift and will only stay in third or fourth gear.

I pulled a tranny code ,code 7 shift control solenoid and so far have replaced both the upper and lower control solenoids with new ones. And no fix.

I also bought a used ebay tcu and swapped it and still no fix. I'm at a loss here as to what it could be and will appreciate any help .

Car starts and drives fine except for the rough shifts could it be the used tcu I bought doesn't work just like the original. I've visually inspected wires and see me tears or rips.

I really dont want to sell this car I really like it but I don't want to put a ton load of more money into it. Please help

 

D4/S light Code 7. Solenoid Valve A Shift Control.

This would be one of the pair of the lower solenoids. Top mounted units are for TC lockup control and not 1-4 shifting.
Verify the connections are clean and tight, sometimes those connectors get a bit sloppy or corroded and those small pins are hard to see. Check for corrosion and tightness, or even make a jumper harness by backprobing both connectors, that is if the D4/S light is still chucking a code.

If no codes are present and the shifting is still rough or even erratic check the following.
Verify fluid is full and within the hash marks.
-With the age of the vehicle the accumulators and gear circuits may be leaking down. Fluid fill looks fine before placing the trans in gear, but with the circuits charged there may be lack of fluid when it comes time to shift, which can cause a delayed or harsh shift. I prefer to place the engine through all the gears after fully warmed up, pull the dipstick, wipe it off, then pull it again(3X) to verify where the fluid is. If you live in a hilly area or where there are off camber turns that can be taken at speed, I've found it to best have the fluid near the top of the hash marks.
Verify the battery connections are clean and tight.
Verify the battery is fully charged. 12.4Volts is a fully charged at rest battery, anything less is a discharged battery. 12.25V battery is ~50% and 11.99V is a dead battery. Low voltage can cause erratic shift behavior.
Verify battery terminals and cables are not corroded.
Verify grounds and bonding jumpers are installed, clean and tight.
Verify the engine is in optimal running condition. If the engine has low compression or other issues, the engine may 'seem fine' but the ECU/TCU will compensate and can cause delayed/erratic shifting.
Verify the NM/NC solenoids are clean. Right side cover two shaft speed(magnetic pickup) sensors. TCU uses these to control upshifting. If they are fouled shaft speed resolution will be lost, code is not always set.
Verify the throttle valve cable is properly adjusted between trans and throttle body. There should be no pretension nor should there be any slack. As soon as the throttle opens the lever should begin to lift.
Verify the throttle valve lever(on the trans) is fully returning to its at rest position. It should not hang up nor sticking.

Open the case to the original TCU. If there are no signs of leaking or exploded capacitors or burnt resistors, reinstall the original TCU. Drive normally, there is a bit of grade logic that needs to be 'learned' by the TCU with your driving habits and terrain.

Finally, verify that the front and rear engine mounts are not damaged. 90-93 use a dogbone front limiter type of mount. And the rear firewall mount is a vacuum controlled hydro mount with a divorceable reservoir. When in park or stopped and engine running the rear mount has a valve that opens and allows the engine to 'float' so there are no excess vibrations that reach the cabin. When the car begins to accelerate the valve closes, reducing the hydro mount to a more common solid rubber, allowing power to be transferred more efficiently. If the controls are faulty(ECU controlled Vacuum solenoid/vacuum hoses/sticking or leaking vacuum diaphragm/broken/leaking mount) the mount will always be in the 'float' or soft mode which will cause harsh shifts as the drivetrain flops around when shifting. Check the front mount first for any damage or wear. It is only designed as a limiter to prevent excessive movement, if it is stretched or damaged then it is probably seeing full engine torque which usually correlates with a problem with the rear mount or rear mount controls.