Cracking ceramic on plugs

what is causing cracked porcelain on my plugs about every 2000 miles. third time 99 ford contour 2.0 cvt. I’m not overtightening.

Are you loosing coolant?

If the ceramic around the firing tip of the spark plug is cracking, this may be an indication of coolant getting into the cylinder. I had this happen on a 1990 Ford Aerostar. The cylinder head had a crack. Fortunately, the vehicle was under warranty and Ford replaced the engine.

Where is the cracking occurring?

And is it on the same cylinder(s) repeatedly?

Fracturing of the ceramics is caused by

  1. thermalshocking (see Triedaq’s post)
  2. lateral stressing of the center electrode during gap adjustment
  3. mechanical shock, generally caused by pinging or preignition
  4. undertorquing, causing poor heat-sinking from the plug housing to the head
  5. overheating. Causes can be myriad, including lean operation.

Your car has an OBDII system. Have you checked for any stored codes?
Have you had any other operating problems?