1989 chevy van 20 explorer

I have a chevy van 20 1989 - the vans has problems starting sometimes, when I do get the van started it seems to sound like it wants to shut off and run at the same time. As I go to put the van in drive it cuts off. Sometimes as i driving i can push the petal to the floor and it only goes about 15 mile per hour. its sounds like its flooded at times also. I've changed the oil, i was to by a shop i dont need new spark plugs, I changed the air filter, coolant, and put gas cleaner in it. Can someone please help me. could it be sensors? how do i change sensors? how many sensors are on a chevy van20 1989. how much will it cost for a shop to change the sensors?

What engine and mileage?
Any codes or check engine lights?
How is the fuel pressure when it acts up and fuel filter?
Is the spark good and blue and hot to all plugs when it acts up?

What is the engine vacuum reading at isle and at 2K RPM?

What engine and mileage?
Any codes or check engine lights?
How is the fuel pressure when it acts up and fuel filter?
Is the spark good and blue and hot to all plugs when it acts up?

What is the engine vacuum reading at isle and at 2K RPM?

thanks for replying, yes the service engine light comes on. Today i tried to drive the van but it was hard to start, and when it started it continuted to shut off. Some one told me to replace the fuel filter and it will take care of it. Does anyone know the steps in replacing the fuel filter it will be my first time. thanks.