Car is a Mazda 6s 2004. My sister's car. She had a cylinder misfiring so we decided to change the spark plugs. We decided to just do the front 3 because it was getting late and they are easy to get to. So I change them, the old ones look ok (maybe a little coating on them but nothing serious) and I also move the ignition coil from cylinder 4 (the cylinder that was having the misfire according to the scanner) to cylinder 5. She leaves and calls and says the problem is still there. So I tell her to pick up a coil. She comes over the next day, I scan, and the problem has moved to cylinder 5. So I figure it's the coil. So I change out the coil. Misfire goes away.

This is where the phrase "If it ain't broke, don't fix it" comes into play.

So I have these 3 other spark plugs that I bought and I figure I should go ahead and change the other 3 plugs so they'll all be the same. I take off the intake manifold. I change out the spark plugs. I get to the second coil bolt while putting the coils back on. It doesn't feel like it is snugging up for some reason. I have my torque wrench set to 55 inch pounds or there about (actually the minimum range on the dial is 120 inch pounds but I figure I am close by backing it off 6 notches - each notch is 1 ft pound). So I keep tightening and then I hear a loud "POW!". The coil bolt has broken in half! Now I'm starting to sweat. So I head to a junk yard looking for a replacement bolt and thinking how am I going to get the remaining bolt out. Can't find a bolt. I go buy some vice grips. I put them on the remaining part of the bolt sticking out of the head. It turns like it isn't even tight at all! So I put a coil bolt from one of the front coils in the hole, and tighten all the coil bolts by hand until they are just past snug. I go to Lowe's and get a M5 bolt that is roughly similar and put that in for the front coil bolt that I swapped. I look at the broken bolt and it is really light (they are all light, like they are made out of aluminum or something). The inner core of the bolt is some kind of black almost porous or crystalline looking metal.

1. Does anyone know where to find a replacement ignition coil bolt? I looked online but found nothing.

2. Was I way off on the torque value?

3. Is there a recommended torque wrench for such low values?

4. Was it a bad bolt? What is that black stuff in the core of the bolt?

I'll try to attach some pictures below. P.s. getting the intake manifold back on was trickier than I thought it would be.

 

a few more images...

 

Really, surely someone knows where to get a replacement bolt or knows the part number? Please?

 

Hi its just a normal m8 bolt . Tighten to 55 in.lb or 6 NM.