1998 ford expedition misfire/ surging issue
 

have a 1998 ford expedition. no engine light comes on, vehicle misfires like or surges especially when cold out. started at speeds of 55 plus , now doing it at 45mph. I had a long block put in a year or so ago. paid $5000 at dealer. just replaced both coils cause they told me it was probably that, but still having issues. thought EGR but runs good at idle and like i said no service engine light has come on. Any ideas, sensors maybe ?

As you are probably aware there are very few problems with vehicles with computers that can be "fixed " shooting from the hip. Many problems require scan tools to observe operation conditions/parameters . We can come up with a list of things to check, but there are no guarantees any of them will correct the problem because it is impossible to see just what is happening with engine operating conditions.
Some of the things you might check,
Vacuum leaks from cracked hoses or PCV system components like the hose or the grommet. A dirty throttle body can cause weird symptoms. A malfunctioning EGR system or component can be responsible. Poor electrical connections also can come into the picture, so as you can see there are many possible causes and without the special tools some of these things can be checked visually.
There could also be pending codes in the computer that might provide some direction.
How long ago were the spark plugs replaced?

does the catalaytic converter sensor really give any feedback
 

I was told i needed to replace the converters on my 1998 ford expedition and that was the problem I was having with it being doggin like and sounding like its misfiring especially when flooring it and going up a hill. Run ok at and idle. The converters are the original, so i know they probably need replacing anyways. seems i replaced the sensor before and problem went away. No engine light comes on but the mechanic says hes 90% sure this is the issue., He put it on the scope and it should nothing no misfire or anything else. Thats alot of money to throw into the truck if it doesnt fix issue . Brother in law was wondering if the sensors to converter really give feedback

There is a simple test to check for a clogged converter. Install a vacuum gauge to a fitting on the intake manifold and rev the engine up to approx 2500 RPM. If the vacuum reading goes down lower and lower, the engine can't breathe because the exhaust system is restricted.