I have a 2001 Ford Focus ZTS, and I replaced all the plugs, and wires, and fuel filter, and just took it to a shop, and since the engine light hasnt come on, they cant find out why the car is coughing during acceleration,and running.
First I would suggest taking it to an auto parts store like Autozone or Advanced Auto Parts and ask them to read the codes. It is not necessary for that light to be on to have readable codes. They would help a great deal if there are any.
This is likely a lean misfire. It could be caused by low fuel pressure, a vacuum leak, egr valve stuck open, fuel injector(s) malfunction. It could be the ignition coil, or ignition control module, etc.
You need another repair shop (which can troubleshoot, and find the cause).