lately my car has idleing at the right speed but it still stumbles when im at a stop light. so i changed my spark plugs and got a valve adjustment but the problem is still there. my CEL is showing code and 1399 and my #3 cylinder is misfiring. what could it be? do i have to change my plug wires as well? thanks

 

change your plug wires with a nice set of NGK's

my friend had the same problem, he bought some crappy plug wires and the ignition was grounding out, I could see the current jumping from the wire to the vavle cover

 

thanks. im definitely going ngk

 

Check the cap and rotor as well. Your fuel injector in cylinder #3 could also be clogging.

 

cool. ill look into that as well

 

I would change the plug wires as JDMdc2lsVtec suggested. Then have a compression test to see the shape that #3 is in and move on from there.