My car is a 1996 Honda Accord 2.7L V6. I am having issues with my transmission shifting rough sometimes. This basically happens when I am in traffic or on a road I can only do 15-25mph and basically it will get stuck in what I am assuming is 1st gear and won't leave 1st until I speed up and then it will shift hard into 2nd gear. I was told by a few people that this is probably not my transmission itself going bad, but instead it is the shift solenoid and if I replace the shift solenoid the problem should go away. Car shifts fine at normal road speeds like 45-65mph. My question is, are they correct? They aren't honda mechanics so I figure I would ask here because I am starting to have doubts in this after seeing some videos on how to test them. My D4 light does not flash like the videos describe and my check engine light is not on. I've already bought the solenoid from eBay. Honda Transmission Lock up Solenoid fits 6-Cylinder OEM # 28200-POZ-003 (99204) eBay

If its not the solenoid, what could cause this problem?

 

Have you checked for any stored codes?
Is the fluid full and in good condition?
Rough/erratic shifting can be caused by dirty or failing NM/NC(shaft speed) sensors. If the PCM is unable to determine what the speeds are actual it will upshift at a pre-programed speed.
Late/delayed shifting can be caused by low fluid, or a faulty sensor on the engine. A faulty TPS may cause a late or no upshift.
Engine condition, if the engine is not running correctly this will affect how the transmission reacts. Engine may seem to run smooth, but the PCM will note a loss of vacuum(via the MAP) and may delay upshifting as a low vacuum would indicate(to the pre-programed PCM) that you are trying to rev the engine/increase speed quickly, delaying the shift.

 

No stored code. I also bought 4 quarts of Honda Automatic Transmission fluid and a crush washer, because I have been doing drain and fills with Castrol multi-import trans fluid and it appears not only was I using the wrong fluid, but I had too much fluid in the trans. I did 2 drain and fills with the honda transmission fluid to try and get as much of the castrol out as possible and now the car seems to run much better. I have only driven to the store up the street from me, so once I drive on this honda stuff for a few days I am hoping to rule out the shift solenoid. Also, I noticed the castrol fluid to be a little black.

After writing this post I did a little research and found the other cause could be the TPS and that in my year honda accord the TPS is integrated with the PCM as one unit. Im not sure if mine is under the passenger carpet like the earlier models, but I did see what you're saying Mad Mike. If my problems persist I may need to get another PCM. As for the speed sensor, I had to replace that when I first got the car because the speedo was not working. So the car has a new one and should not be failing. My speedo still works.