First, what engine do you have? 4.0 and 2.5 don't really have a PCV, just a fixed orifice to vent the crank case with manifold vacuum. Even if you switched out the CCV , did you check to see if vacuum is getting to the grommet? If it is a 4.0, there may also be a flapper valve below the grommet that can get stuck closed with grunge causing same issue. Easiest thing is to remove cover and clean out thoroughly.
As far as the timing chain fixing blow-by :huh???: