is necessary to change the 4 coils , if only 2 of them have the white staff on the bottom?

 

white marks do not mean that coils have failed. its best to replace them all together. factory coils tend to last about 30k give or take. you can invest in the bhr kit and you wont have to replace them again

 

ok.. thanks. so u never know if the coil is bad??!!!!

 

Mazda released some info on how to test the coils, but their method is just a bit too conservative. in the other words, it might fail to catch "failed" coils.

White spot doesn't mean ****.

If you replacing 1, might as well replace it all and be done with it.

 

ohm test. Utterly useless.

 

Mine went out completely at 35K but started acting up in hind sight at around 32K. That burnt small you noticed was the underside of your car being cooked. When mine failed I was driving home and the car lost power and was running very poorly, after about a mile I noticed the burnt small. I pulled the car over an looked underneath and the CAT was glowing orange. Apparently since the coils are not firing the fuel in one of the rotaries is not igniting and is being dumped into the exhaust where it is then burnt in the CAT.

So if the car starts running really rough and loses power don't drive it or you'll fry the underside of the car.