Changed one spark plug, now blows 15a alternator fuse when put in drive

[Noetown]

Hey guys, I've found a lot of wonderful tips here for minor repairs I've needed. Now I'm in dire need of help! I have a 1996 Ford explorer Xlt with the 4.0 v6 automatic. Earlier today I changed one spark plug because it was the only one I could get to before I decided I'd be better off letting a mechanic do it. The vehicle will run fine while idling in park but as soon as I put it in drive voltage gauge drops and the battery light comes on. Every time this happens it blows the 15a alternator fuse under the hood. Can anyone tell me what I done wrong and if i can do anything to fix it please?

 

[Machine090767]

Put the old spark plug back in and see what happens.
Replacing one plug should not cause the trouble you are having.

 

[Turdle]

If by chance the one plug you did change was on the driver side rear, go see if you knocked the transmission wire harness loose and it is in contact with the exhaust.

 

[Machine090767]

^ I never thought of that.
Smart man.

 

[Noetown]

Put the old spark plug back in and see what happens.
Replacing one plug should not cause the trouble you are having.

The old plug was broken

 

[Noetown]

If by chance the one plug you did change was on the driver side rear, go see if you knocked the transmission wire harness loose and it is in contact with the exhaust.

I changed the driver front and driver rear. After changed the driver rear it seemed to have fixed the problem with it blowing the fuse. I'm going to change the rest of the plugs today hopefully. It was idling really rough originally, it sounded like a diesel lol