Pontiac Repair: engine running rough, pontiac gran, head gasket

Question
Hi,
A friend has a Pontiac Gran Am Quad4 1998 2.4L.
after noticed that the engine was not running right I removed the spark plug, and # 2,3 were black but not oil, just carbon deposit. changed the plug,and the same thing happens.
Thank for your help

Answer
Hi Efren:

well those 2 cylinder share an ignition coil. You could have an ignition coil that is bad or an ignition module that controls the coil bad or lastly the housing that the coils sit in the plastic piece may be bad the coils will crossfire inside that housing and cuase the issue you have. The cylinder are lacking spark is my guess or they could be lacking compression. if you have a compression guage check the compression in all 4 cylinders if 2 and 3 are low it may have a head gasket blown between the 2 cylinders. Good luck :)