General questions

Greetings, all. My name is Ian =) Hope everything is well.

I have a small list of things that are bothering me and I would be most appreciative of any advice.

I drive a 1996 Ford Thunderbird. I love the car to death, thus it saddens me to see it acting like this =D The car was my father's, but considering it's age, it has a relatively low mile count on it. Just a little over 100,000 miles, which was reached around december. The car sat for a few years because my father had a company vehicle. The engine is starting to show aging problems and I'd like to counter them before they get too bad. The car is stuttering between 2nd and 3rd gear(auto) The whole block shakes and I have to get off the gas pedal so it'll stop. Acceleration and speed wise? The car does not pick up like a V8 should. It feels like I'm driving a civic. However, the issue is not constant. Sometimes the car gets up with incredible performance.
Also, there's a rattling ... sounds like in the front left of the car. It sounds similiar to what a piece of rubber jumping up and down in a glass jar would sound like. Perhaps something dropped off.. or came off?
Thank you for your time.
-Ian

Welcome to the forum!
It's probably time for a tuneup, to begin with. When were the spark plugs changed last and did he ever put new plug wires on and change the filters?
The shaking can be caused by the transmission. Some people in this forum have used Seafoam additive in their transmission to help clean it before replacing all of the fluid (don't forget to drain the torque converter) and filter. Go about 1/2 way down on the first page of the Tech help thread and you will see a post titled GETTING RID OF TRANSMISSION SHUDDER (4R70W 94+) to see if your symptoms are the same.
Take the car to an alignment shop and have them check the front end components. There are several things that could be loose so it's better to have someone look at it then try to guess.

I would aggree with 97. That its probably the engine is not running well. The(misfire) condition can really be aggrevated and very pronouced when the torque converter clutch is fully locked up.

If you where having symtoms of a torque converter clutch problem from lack of ATF integrity. Then you would have a very fast (like driving over washboards on a dirt/gravel road) vibrations around 35-50MPH, depending on throttle angle. But still have good power and pull.

I'd shoot for a full tune-up and maybe a fuel injection clean too:).

Thanks for yout advice. It's greatly appreciated.
Cheers,
Ian.