Originally Posted by DRHouse822

The 97 still ran a cap and rotor distributor, so it is impossible for it to fire two cylinders due to mechanical issues that's good news for you. ? are you using the factory spark plug wire guides, if not it is possible that wires 1 and 5 are crossing each other causing both plugs to fire this can happen even if the spark plug wires are not frayed. If it is this, it would be intermittent due to fact if the wires move just a little it will cease to cross fire. Now for the PCV Valve, the 4.0 never ran a PCV it ran a CCV Valve, which is a fancy way for saying "open tube". I grew up back East and just like Sacramento there is a lot of moisture in the air, this will mix with oil vapor in the CCV tube forming a thick milky type residue. On the early 4.0 it would saturate your air filter with in 15000 miles, due to the fact the larger of the two breathers goes in to the air box.