car problem. 94 ford escort. read details for info. please help?

[George]

i need help. i have a 94 ford escort lx with 150,000 miles and it sounds like the engines popping when your driving and sometimes when your idling, just changed plugs, gas filter, pvc valve, air filter. still seems to be running the same way. also there is no check engine light. could it be a fuel injection problem? iv added dry gas and injector cleaner to a full tank of gas a couple of times and still no results. please help