audio wiring 93 ford taurus

I've just replaced the factory speakers, and both on the rear panel work great. But after five minutes of driving my front two both cut out almost completely. The front right speaker is very distorted, and there's absolutly no sound coming out of the front left. Mind you both rear still work. I've pulled the door panels off and the connections are ok. (on my old set of front speakers the connector on the right door panel was partially melted) I thought maybe the wires were being grounded out by the door itself or each other, but they're covered completely. Does anyone have any suggestions....?

I had a vehicle once in which I was doing door speakers, and the vehicle had previously been in an accident and had the door panel replaced.  Whoever replaced the door panel did not know how to get it to stay in correctly, and so they just decided to put a screw through a seemingly innocuous spot on the door panel.  Turns out they went straight through the speaker wiring.

It took me forever to figure this out though because when you look at just the speaker connector and all of the visible factory speaker wiring it all looks totally fine and appears normal.  Once I put the door panel back on and put that screw back in though, the head unit would go into protection mode (sound cuts out), until I removed the screw.

Sorry for the digressing but my point is that even if the wiring may appear to be in good condition, there are always areas/lengths of wire that you will not be able to see; unfortunately, just because you can't see that particular length of the wire doesn't mean the problem doesn't exist there.

It really sounds to me like there's a problem with the speaker wiring inside the door or with the terminals touching bare metal intermittently.  I know this is probably not what you were hoping to hear but I'm pretty sure that's what's going on. 

Of course it's always possible that the problem exists in the speaker wiring up behind the head unit but since your rear speakers are fine and you didn't even mess with the head unit when you did the speaker install, I think that is very unlikely.