High rpm concern

[91DSMnoob]

Hello, I'm new to posting on this site, and pretty new to car maintenance in general and dsms especially. I have a 91 turbo laser 2.0 automatic with no aftermarket parts (kinda broke right now). My concern is that I feel my car has an issue with the transmission. When i start the car, sometimes it revs high then will bog down and rev back up again. I found out that if I wiggle the shifter the car returns to normal. When I get on the highway, my car is at about 4500 rpms around 60-65 mph, and climbs to about 5500 around 70-75. As soon as I let of the gas my car Quickly loses speed and drops rpms. I feel like this is really hurting my gas milage as well. I was wondering if this is common, and if not how i can fix this. It has a bad exhaust ( and manifold I'd assume) Not sure if this has anything to do with it?
Thank you
(Like I said, I'm new to this so don't be too harsh)

 

[Phantom DSM]

You mention that your car is at 4500 rpm on highway cruising 60-65. Do you have the O/D button disabled on the side of the shifter, You are stuck in lower gear, It should cruise at a lower rpm when you are in 4th gear(Overdrive)

Also does your idle in park surge up and down in rpm higher than 750? Bad exhaust is an issue as well if you can explain where the leak is from ?

 

[91DSMnoob]

With over drive on or off, It usually does the same thing. Could it be a broken over drive problem? Going from my house to campus and back mostly highway at about 60-65 mph (about 7 miles) I burn under an eight of a tank of gas. I feel like if i fix this my gas milage will improve alot.

and it used to be alot worse, after I found out about the idle screw, that solved it from being about 2000-2500 down to about 1000-1500. Like I said it hasn't been acting up since i figured out about messing with the shifter (not sure the proper name) so I was wondering if maybe a cable was loose from the shifter to the trans?

My goal is to first replace the manifold (I hear that 2g ported ones are best, not sure how true this is?) and back. Maybe a 3 inch system (not sure the different types of exhausts and how they affect performance?

You mention that your car is at 4500 rpm on highway cruising 60-65. Do you have the O/D button disabled on the side of the shifter, You are stuck in lower gear, It should cruise at a lower rpm when you are in 4th gear(Overdrive)

Also does your idle in park surge up and down in rpm higher than 750? Bad exhaust is an issue as well if you can explain where the leak is from ?

With over drive on or off, It usually does the same thing. Could it be a broken over drive problem? Going from my house to campus and back mostly highway at about 60-65 mph (about 7 miles) I burn under an eight of a tank of gas. I feel like if i fix this my gas milage will improve alot.

and it used to be alot worse, after I found out about the idle screw, that solved it from being about 2000-2500 down to about 1000-1500. Like I said it hasn't been acting up since i figured out about messing with the shifter (not sure the proper name) so I was wondering if maybe a cable was loose from the shifter to the trans?

My goal is to first replace the manifold (I hear that 2g ported ones are best, not sure how true this is?) and back. Maybe a 3 inch system (not sure the different types of exhausts and how they affect performance?

 

[Phantom DSM]

Looking at a FSM the overdrive is controlled by the TCU by receiving on and off signal from the auto cruise control unit. Can you check fuse #7 labeled HEAD and #9 labeled 4A/T on fusebox cover, both 10 Amps. If they are good, then we can check further to get Tcu codes using this link TCU Codes, Puls generator B is usually associated with this.

 

[91DSMnoob]

Looking at a FSM the overdrive is controlled by the TCU by receiving on and off signal from the auto cruise control unit. Can you check fuse #7 labeled HEAD and #9 labeled 4A/T on fusebox cover, both 10 Amps. If they are good, then we can check further to get Tcu codes using this link TCU Codes, Puls generator B is usually associated with this.

I checked both of them and they are intact