alright... so i have a strange problem.

when i turn my car on every once in awhile i get a strange high pitched whine... so first thing i think is bad ground... but here is the wierd part. It just gets louder and louder until it makes a loud pop in my front speakers. Im thinking if i had a bad ground it would be constant. Besides, it just started out of no where. Second thing is the front speakers seem to fade in and out. I will be driving along and the front speaks will get way louder and higher. But its temporary. Alright... so things im thinking are:

1. Maybe it is a bad ground (im going to reground the amps this week)
2. Maybe an impedance mismatch between my amp and front speakers.

any suggestions on what to check when im tearing apart the car this week?

TIA