Three suggestions:
1) Buy an OEM manual; best investment you will make.
2) Read the Top Secret files at the top of this forum. There is a wealth of information and some great tips for effective troubleshooting.
3)
"and replaced the Plug several times"
In general, if you replace any part several times without getting any positive result, you are just guessing, and would be better to just open your wallet and your car window and throw the $$$$ out and get it over with....
I know it is "only" spark plugs in this case, but that is still ~ $10- each time, and I'll bet that you've thrown out at least 4 perfectly good plugs.
Systematic troubleshooting will get you to the root cause of the problem and you'll know what really needs to be replaced....if anything.