'71 280se downshifting issue
Hello, I am new to the forum and need some advice. I am the second owner of a 6 cylinder '71 280se sedan with auto. transmission. It has 98k verifiable miles (I have all books and records and every repair receipt). The prior owner took meticulous care of the car, and so have I. It is absolutely gorgeous and runs like a champ. However, when downshifting from 4th to 3rd, it seems to hang too long in 4th and "jerkily" shift to 3rd. (Downshifting from 3rd to 2nd is also sometimes jerky, but not as bad and not as often.) For instance, sometimes when I am in 4th and back throttle by removing my foot completely off of the accelerator, the car stays in 4th for what seems to me to be too long and then when it downshifts, it will briefly (2-3 seconds) bounce in and out of 3rd before staying in 3rd. As you can tell, I am not technically inclined; so I am just describing how it seems to me. I have learned that I can stop the "bounce back" effect by keeping some pressure on the accelerator as it downshifts. Even when I do, it still seems to hang too long in 4th and jerk when it downshifts to 3rd. I have consulted the service manual and am wondering whether it could be some problem with the pressure control linkage. I am praying that it is nothing more serious; I love the car. Can anyone help?
One other issue. There seems to be an issue with the two-way valve that controls the idle speed at low and high temperatures. It used to be that when the car cold started, the idle speed was increased, and after the car warmed up a bit, the two-way value would "click" (audibly) and the idle speed would decrease. Recently, when the car cold starts, the idle speed stays high even after it has warmed up. In fact, even after having driven the car all over town, when I put it back in park, it will sometimes be idling too high. In both instances, I have left the car running, popped the hood and just flicked the two-way valve with my finger. And immediately the idle speed drops down to normal. What do you think? Maybe a stupid question, but if the valve is "sticking," is there a way I can clean it. (Since I am not a mechanic and cannot do much more, I am really into cleaning.)
Also, any advice on a repair shop/person in the Fort Worth, Texas area?
Thanks for any help.