Ford Repair: Auto Repair, auto repair question, carbureted engines

Question
QUESTION: Hello,

I have a 94 Ford Escort.  I would like to know your thoughts on hearing the following:

After starting the car from cold, then driving the car on the highway for about an hour, on getting off the highway I am immediately unable to go any faster than 20 - 25 miles per hour.  

After driving around for 20 minutes trying to get the car to go over 25 mph, I then stop the car for several hours, let it get cold, and I am once again able to drive the car normally.  

Then, after getting back on the highway, driving around 60 mph again for about 30 minutes, as soon as I get off the highway, I am unable to go any faster than 20 - 25 mph, until about an hour later (of driving at 25 mph) when it finally kicks in and I am able to drive normally again.

Does this sound like something that makes sense to you by what I am saying about it?

Thank you

ANSWER: couple questions, is this an automatic or standard trans ?? also, what is the air temperature where you are ????

---------- FOLLOW-UP ----------

QUESTION: It is an automatic, I do not have to manually shift.  Also, I am in the DC area which on that day, it was early in the morning and their was frost on the car so I estimate that it was at least 30 degrees that morning, but later in the evening upon my return, it was likely a bit warmer like say 40-45 degrees or so.

Thank youf

Answer
without actually being there I'm gonna give something to try as this  was a common concern. find your air filter, there will be a plastic hose type connector that leads to the outside air ( the air that feeds the air filter box.) remove it. go to your local auto parts store. buy a piece of flexible aluminum hose about 2" in diameter ( looks like hose you would hook up to a dryer ). if you've ever seen the old carbureted engines, they had this type of hose coming from the exhaust leading into the air filter. ask your guy at the auto parts store for this. insert it into the hole that you took the previously mentioned piece of hose you removed from the outside air inlet to your air filter. take the other end and place it as close to your exhaust manifold as possible, secure it in place by what ever means you can. what i think is happening is your air flow meter is freezing. this sensor monitors how much air and the density is entering the engine. The idea is to try to warm the air entering the air filter housing where this sensor is located. i know this sounds complicated but very simple. try it and get back to me.