I have Denso iridium 0.4mm IK20#4 spark plugs.

are these fit 03 wrx?
I have lean codes, do you think I can get rid off the codes by changing the plugs to smaller gap?
Wrx stock gap is 0.7 right?

help.... thanks

I have Denso iridium 0.4mm IK20#4 spark plugs.

are these fit 03 wrx?
I have lean codes, do you think I can get rid off the codes by changing the plugs to smaller gap?
Wrx stock gap is 0.7 right?

help.... thanks


....that 0.4mm is the diameter of the center electrode....NOT the gap.

....they will fit an '03 wrx

....yer lean code is NOT caused by the plugs....an intake(leak) most likely.

....proper gap will be 0.7mm - 0.8mm

BEWARE gapping these plugs....if you do not do it EXACTLY the way it is supposed to be done, you will DESTROY them.
You can NOT touch the center electrode with ANY force or you will break it off.......ask me how I know this. :rolleyes: :(

Ok, so what is that 0.4mm in my plugs?
before i get more confused, what is gap exactly?

I have stock intake. I dont think there is any leak.

....that 0.4mm is the diameter of the center electrode....NOT the gap.

....they will fit an '03 wrx

....yer lean code is NOT caused by the plugs....an intake(leak) most likely.

....proper gap will be 0.7mm - 0.8mm.....0.028"
BEWARE gapping these plugs....if you do not do it EXACTLY the way it is supposed to be done, you will DESTROY them.
You can NOT touch the center electrode with ANY force or you will break it off.......ask me how I know this. :rolleyes: :(.....

Ok, so what is that 0.4mm in my plugs?
before i get more confused, what is gap exactly?

I have stock intake. I dont think there is any leak.


Gap is the space from the center electrode to the ground arm. Or simply the gap inbetween the thing in the middle and the little arm on the top.

is it always necessary to gap the plugs each time changing them?
I thought it's always like 'plug ang play'

if your air flow meter is like the newer cars, check your air flow meter. i seen them covered with dirt and dust and cause an incorrect reading to the computer. take out the two screw and with a flash light, look inside and you will see two wires. check them and make sure they are clean and not covered with oil or dirt. if they are, clean them with contact cleaner that can be bought at an auto parts store and put them back.

My A/F reading keep changing.. but most of the time it shows 0.01 and sometimes 0.00.
Is this normal?
When the reading show 0.01, my battery volt goes down. I dunno why.
Sorry I'm noob, just got the car for 2 months.