#4 misfire and running rough

I have a 1999 Windstar 3.8l. I have a misfire in the #4 cylinder. The van runs real rough. I pulled the intake and replaced all the gaskets. I had the TSB done a while ago(.. reprogram PCM, bolts, valve cover, ect...) The EGR ports were alittle plugged. I cleaned them out and put it all back together. I still have the misfire. When I rev-up the engine I hear a loud sucking of air noise. It was making this noise before I pulled the intake as well. Any suggestions for the problem? I would really like to fix this myself.

Topher, if you can isolate the sucking noise, it sounds like a vacuum leak.

No guarantee that will solve your misfire problem, though :)

Check your spark plugs, plug wires. Look at the plugs and check them for fouling, that could be an indicator of more serious problems. Make sure you injector on #4 is working.

Good luck and let us know what you find out.

You can always swap injector #4 with another, if it still misfiring on #4 than you know it's NOT the injector, but definitely try to find your vacuum leak.