Missing, bucking and some back fire.

I ran 2 full tanks through it and it ran fine. Now on my third tank it has started to hickup, buck and last 2 days it seems to be running on 3 cylinders. It idles rough. Gas company is big and goes through a lot of gas. My wifes Taurus uses the same gas and has not had any problems. While drifting in low gears it pops out the exhaust. Original owner told me it got new plugs 2 years ago. ( 20k miles ago ). I put in a new air filter. I put in a bottle of injector cleaner just in case. Check engine light blinks and stays lit when I stop. I believe it has the original timing belt.

Anyone had this problem? If so what was the cure. I haven't worked on cars for years and hate to go to Ford and get charged up the wazoo.
Thanks for any info you can offer.
Have you considered changing the fuel filter?


