98 explorer cold idle problem

I have been having a problem with rough idle in cold weather even after the car is warmed up. I was wondering if it is a IAC valve problem.(I checked it with a elec. meter and it is well with in limits at 10 ohms of resistance) But I am wondering if it could be dirty or sticking. My other question is could it be a DPFE sensor even though my check engine light has never come on. The engine is question is a 4.0 SOHC. I did have the recall done last year that involved the gaskets.