car idle will not hold steady. Will not accelerate over 30 miles per hour; on 1998 Ford Escort

that 30 mph takes a mile to get there

3 answers
Possible clogged catalytic converter or restrictive fuel filter ,don't
Know history or miles??
Does it miss really bad. Not running one all cylinders, possible coil issue.
Should be easy for a tech to figure out in 30 minutes. Likely are collapsed cat converter/exhaust pipe or faulty ignition coils or ignition module. Is it up shifting, if an automatic. IF not a possibly failed modulator on trans could be problem. When you post a question, the more information you post, ie mileage, transmission type, any previous diagnosis, can help and will get you more and more accurate responses.