I recently carried out a compression test on my 240z engine and the result was perfect. Nevertheless, last sunday i left the car idling with the Hood open for 10 to 12 minutes and the engine started to idle roughly. I then decided to drive the car and the engine started missing at 2nd and 3rd gear. Surprise, when i got home i pulled spark plug 3 and 4 and both were black fouled. The other ones looks okay. If i already changed the spark plug wires, cap and rotor and the compression is good what could be causing this? Should i use some nose pliers to tighten the terminals?