No. Get a new plug.
==================
Yes to above but if you can't then wash the plug in petrol (gas) - (be careful when doing this as there is a danger of fire). Then use fine sand paper to clean up the electrodes and a feeler gauge to reset the spark gap.
Wear. Fouled. Cracked.
no The starter should engage whether the plugs are fouled or not. However, the engine may not start if enough plugs are fouled. If you feel that you have flooded the engine or fouled the plugs you may need to clean them before it will start. If you have caused the carburetor float level or other settings to be significantly changed, the engine will flood and it will not start.
if the spark plugs are black because your car is running too rich. your plugs are fouled.
Fouling spark plugs can happen when the tip temperature is insufficient to burn off carbon, fuel, oil or other deposits and causes spark to leach to metal shell...no spark across plug gap will cause a misfire. Wet-fouled spark plugs must be changed as they won't fire. Dry-fouled spark plugs can sometimes be successfully cleaned by bringing the engine up to the operating temp.
Yes, fouled spark plugs can cause engine shaking, and loss or power. I'm not sure about knocking but I'd guess that too.
make sure your air cleaner is clean,also check for fouled spark plugs
Spark plugs do not loose power, rather, they become worn and erroded. On occasion they may also become fouled, indicating a mechanical or fuel problem.
You should check your spark plugs periodically as they can give an indication as to how your engine is running. If the spark plug is fouled the engine wont work as efficiently as it's supposed to. A normally operating engine should result in a light brown discoloration, check your spark plugs against a reading chart like http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp If the spark plug is fouled or eroded, replace it. It's a simple job and spark plugs aren't too expensive.
spark plugs fouled with oil. blue smoke from tail pipe.
You have to remove them and inspect.You have to remove them and inspect.
if it's runninng rough my guess could be spark plugs are fouled up. if not then next check the spark plug wires then the distributor.
possible fouled spark plugs, bad fuel. check both and if both are good, get back to me.