1993 Ford Aerostar Engine Stutters

Van starts up and runs normal. After running on the highway for a while and then coming to a stop or even just accelerating it stutters. Check engine light use to come on (it would go on and off) until I replaced the O2 sensor but the engine still stutters. I also leak anti-freeze internally (but no smoke out the exhaust)(I can go about a month and the radiator will be around half empty), so I thought it was the head gasket and put barsleaks in the radiator and ran it for half an hour with no change. I do have to watch the engine oil but again there is never any type of fluid under the van when it sits and again it never smokes. I did notice the valve covers have oil on them but right now I worried about the hesitation. This is our only vehicle and it's dangerous when you have to pull out when cars are coming and the van will not go! I was going to check the fuel filter but cannot find the switch the haynes manuel tells me to disconnect to releive the pressure. Any suggestions and thanks for the help!