OK, I've been fiddling with this for 2 hours and I'm fed up, but I need your help and I'm willing to mail you a beer or something if you can help me diagnose that stupid issue! I've read other similar threads and I'm 99.9% sure it's a ground issue, so basically, I need an Acura TSX 2004 expert to identify every single stupid ground location on that car because I definitely am missing one!
The car does NOT (always) crank, but sometimes it DOES (very random).
The car mostly does NOT crank on humid weather, like after rain even up to the next day after rain.
WHAT WE ALREADY KNOW:
When it DOES crank, it runs perfectly, no stutter or anything for any distance but turning the car off at that point is a 50/50 chance of it not cranking anymore, even if you leave it only 1 minute not running.
When it does NOT crank, it makes clicking (relays) sounds like crazy, sometimes only once or twice a second, sometimes 10 times a second, like super fast and it's really totally random, meaning if you leave the key to the start position, it will do like click-click-click... nothing, click... nothing cl-cl-cl-cl-cliiiiiick click... (lol)
Additionally, when it does NOT crank, I can actually SUCCEED and start it by leaving the key in the start position and keeping my foot pushing down the clutch for 30 seconds, sometimes 1 or 2 minutes and eventually the car will end up cranking out of the blue and starting just fine, without actually releasing the key and trying anew. It's like it's trying 10 times a second to start it and there's only 1 chance out of 1000 that it'll actually crank.
The battery is an orange top 350A, 9 years warranty, only 4 years in and it gives 12.9V with a multimeter, when the key is off. Doesn't make any difference to leave it on the charger for 4 hours at 6A, still same relays clicking sounds, same thing.
The battery terminals are spotless, shiny, very firmly secured and they've been cleaned up this morning, the wire connectors also are shiny like new.
No check engine light.
The starter is 2 years old, less than 30,000km.
THE GROUNDS I'VE CHECKED:
The ground harness that goes from the passenger side triangle engine mounting bracket was not looking very nice like half spliced up (altough not entitely), so this morning I unscrewed it and replaced it with a brand new subwoofer ground wire, it's stamped for high voltage on the enveloppe and it's well secured both on the engine mount and to the passenger side OEM attachment bolt. It's giving the conductivity beep on the multimeter.
The battery NEG pole that is tied to the driver side body is firmly attached, and was also cleaned this morning, it's also giving the conductivity beep when bridged with the multimeter, so I know it's good.
I know there are more than 2 grounds on that car, but I don't know where they are and how to properly reach them (the passenger side ground bolt was a F*** pain to remove!) so please if you can post pictures and instructions, it would be very much appreciated! :D