I just bought a 2005 forenza. It runs good but usually wont go into 4th gear. when it does it will not downshift at a stopsign and wants to take off in 4th gear until it's cut off and restarted.
It sounds like you have a trip to the tranny shop in your future. It's not going to get better and will only get worse. If you are not afraid of pulling the transmission yourself you could take it out and bring it to the transmission shop to probably be rebuilt, if nothing else to replace 4th gear.
I think the transmission shifts too well in other gears to be bad. It seems electrical to me. when it gets to 4th and won't downshift, I can cut off the car and restart and it goes back to shifting normally. I suspect the is a solenoid for 4th gear that is not working properly. R&R on the tranny is no big deal, but I don't want to unless I have to.
P.S. already changed the range sensor
Wow, I expected more thoughts on this one.....
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