also another problem idles rough when I turn the heater on.

[amys4x4explorer]

When I turn my heater on my vehicle idles rough, would that have something to do with a oxygen sensor being dead, and dearly departed?

 

[bikeboy]

Amy, I have a 99 SPORT 4.0 sohc. Mine has a LOW 50K miles and has ALWAYS done the same thing. It is most likely the same symptom that you have when you turn on the A/C in the summer??? Most likely you are experiencing compressor drag on the engine. On Exp.s the compressor cycles when the heater is on. Hope this helps.