Originally posted by: SupaDupaCheez
I'll tell you how to figure out if you need a new cap and/or spark plug wires:
1. Take your car to a VERY dark area (inside a closed garage would be fine)
2. Open the hood
3. Start the car (make sure the emergency brake is on or it's in park)
4. Look under the hood (be carefull of the fan.....it is dark you know

)
5. If you see sparks coming from the cap and/or wires.....YOU DEFINITELY NEED TO REPLACE THEM (these 'sparks' will probably be a little hard to see)!!!
I asked a mechanic the exact same question when I was 18 (i'm 34) and had a honda with over 100k. He showed me this 'trick' and I was amazed at how much energy was lost due to a cracked rotor or old wires. Lost spark means that your engine is either working harder to burn the fuel or it is just passing the fuel on to your Catalytic converter (either way means a loss of MPG). Needless to say....I now make sure that my wires/cap/rotor are changed at LEAST every other year.
CLIFFS:
1. Just change them
SDC
PS: Make sure you only run the car for a few seconds inside that closed garage...wouldn't want a post from your parents tomorrow accusing us of 'killing you'.