#4 misfire and running rough

[Topher1]

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.

[Dngrsone]

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.

[Rowdysrides]

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.