A42.0rgy

what are some causes and effects of bad spark plugs?

Yippers®

fire at all, good idle w/ misfires at higher RPM, poor idle with misfires at speed.. etc

A42.0rgy

and give me a little more info on what exactly what causes a misfire and what it is?

Thank you so much

Yippers®

Spark plugs are designed to come to specific tip temperatures in use. This is called the heat range. It is set so that at operating temperatures the tip will be just hot enough to burn off carbon deposits, etc. If you use a plug that is too hot the fuel/air mixture may well pre-ignite .. ignite from latent tip heat rather than from the timed spark. A plug that is too cold may foul with carbon or unburned fuel deposits because it lacks the heat to keep itself clean. Deposits may also create hot spots that can induce pre-ignition.
If a cylinder is leaking sufficient oil past the rings or the valve seals plugs may foul from the oil .. much harder to burn oil than fuel. Fuel fouling can happen from excess fuel .. bad injector, poorly set jets on a carb and such. Flooding is an extreme example of this.
Misfires are either a partial ignition of the fuel/air mixture or a complete failure. A bad plug, too rich a fuel/air setting, a bad coil, bad ignition amplifier or a gap that is too large are some examples of misfire sources.
The width of the gap that the spark can arc across is is determined by the voltage to the plug and the cylinder pressure among other things. The higher the cylinder pressure the more voltage it takes to arc the gap. The ideal gap setting on a plug is as wide as possible without causing misfires (failure to ignite or sustain the flame front)at the maximum cylinder pressure. As you increase boost you increase cylinder pressure and that optimally wide gap needs to be narrowed a bit as the spark may well not be sufficient at the wider gap to sustain the ignition .. the flame front may 'blow out'.

A42.0rgy

1.intermittent misfires
2.failure to fire at all
3.misfires at high rpms
4.poor idle

Thanks SO MUCH