Need help regarding Rough Idle

I have a 95 Dodge Neon Hi-Line SOHC it was running rough so I changed the spark plugs and put in some Champion copper plugs with a .45 gap. When I changed the plugs I found oil in the number 4 spark plug well so about 2 weeks later I replaced the o rings and gasket this helped the rough running a bit at first but it was still running rough so today I went out and changed the plugs again and this time I out in NGK G-Power platinum tip plugs with a .40 gap. The car started fine ran great while cold but once it heated up it started idling rough again but runs smooth and now I do not know why:banghead: . I checked the spark wires and they are good can anyone help? Is the gap too small perhaps and would this cause the problem?

Thanks

Too small of a plug gap can certainly cause misfiring, but not until you are way down below the normal range - maybe less than .020". I would think the rough running icould be due to a vacuum leak or PCV or EGR not working right.

Thanks for the help what is the easiest way to check to see if the problem lies with a vacuum leak or PCV or EGR not working right?

By inspection - check on the condition of the rubber line going from the intake manifold to the PCV valve (on my 97 its behind the curve of the intake manifold) and the line from the valve to the top of the engine. Also check any other vacuum lines - all of which would start from the intake manifold or the throttle body. There is a vacuum line going to the brake booster - which might be loose or coming apart.