I just went thru speaker replacement on my GXP, the rears were difficult to wire in using the factory amp. I would think on your car since it comes and goes they are probably wired correctly, but maybe check the wiring for loose connections. You didn't say if this happens in the front or rear, I'm guessing its the rear 6 x 9. This is a decent thread about wiring the rears. Good luck, post back your findings.

http://www.g6performance.com/forum/s...ad.php?t=18003