Idle drop, knocking sound

Yesterday I was in the drive through line and the idle dropped to 3-4 hundred RPM's. As soon as it dropped the car started making what sounded like a rod knocking. The RPM drop and noise only lasted a second and the went back to normal idle with no knocking sound at all. This is the second time this has happened. Is this something I should be concerned about? 2001 GT.

The last time my car ran before today was the time I mentioned in my first post. Yesterday I was going to use it to run some errands and it would not start. Would turn over good but would not even act like it was going to crank. Today I laid under the car by the gas tank and had my son cycle the key from the off to run position and no fuel pump sound at all. I pulled the air tube loose and sprayed a little starting fluid in the throttle body and the car would run for a second or two. I checked all the fuses and all were good. Next I went inside the trunk to the fuel pump shut off switch. The button was in the run position. I then pulled off the wire plug and ran a jumper wire across the plug to loop the two wires. The car started right up after doing this. I then just put a wire connector and connected the two wires together to bypass the switch and took my car on a 20 minute ride. Car runs good and for now my idle drop is gone. I wonder if the switch going bad was momentarily shutting off the fuel causing the drop? Has anyone else had a fuel pump shut off switch go bad?

I will do the voltage drop test in the next couple of days. Have a very busy day tomorrow. Would be interested just to see the results. I noticed when pulling the large fuses under the hood most of them on the plug in parts looked like they had been exposed to excessive heat. Most were discolored from heat. Would that be a sign of voltage drop or is that normal for those fuses? Thanks