If your check engine light is blinking that means an ignition misfire has been detected
A car that is stopped with the engine running.
Yes, "sparkling plugs" is definitely detrimental to idling or smooth running of an engine
Have it checked for codes. There will be a misfire code that will let you know what cylinder has the problem.
13.5 to 15.5 volts with the engine idling.
Idling is what your car is doing when it is just sitting somewhere running. As soon as you press on the gas it is no longer idling. Your idle speed is the number of RPMs your engine runs at when you are idling.
Yes, idling in park.
If your car is shaking while it is idling, it is most likely your automatic choke. The automatic choke is not operating correctly but if you remove the choke and put a lubricant on it, it should stop shaking.
misfire
You most likely have cylinder misfire. Check your ignition coils and spark plugs.
Defective cooling fan or bad fan relay.
Check your vacuum lines this usually the cause for a surge in engine speed when idling or running.
With key on engine off 23-31 psiWith engine idling 13-20 psi