I'm pretty sure something is going to need changing. My 2004 RX8 has been good and bad. Yesterday, It started right up 1-2 seconds all day on cold and hot start. The day before it had mixed reactions. Today I'm thinking I'll pull it into the garage, so I do the whole turn to acc wait then crank. It doesn't crank at all for the first 3 seconds, so I stop and try again for 2 more times. So not to damage my starter and drain my battery, I give up and go in for breakfast. After breakfast, I go again and starts up right away.

I've done the diagnosis listening to noises or symptoms that show compression loss. My rx8 has no power loss, it starts up perfect for 80% of the time cold or hot.

-2004 mazda rx8
-77xxx kms
-nothing has been changed in terms of battery, coils, sparks, plugs etc. Still running on the stock starter as well. I'm guessing that its wayyy overdue. Idk if those could affect start up 20% of the time.

Going to get it serviced, compression tested and doing the whole 30k miles maintenance schedule as recommended here in a couple of days. Wanted some opinions on what it could be.

 

Sometimes not even cranking, but other times starting up fine ... is the battery connections. The connection is poor, sometimes it gets enough current through to turn the starter, sometimes it doesn't.

Remove both battery connections, clean the clamps and posts, don't forget the inside of the clamps, and make sure the clamps are seated correctly on the posts as you tighten. Wiggle them around to make sure they sit somewhere that they want to. And make sure you aren't just bottoming out the tightening bolt/nut, because you can just tighten the clamp against itself.