couple of days ago i notice my dts idling very hard........ and i could sometimes smell gas...today the engine light came on and flashed..... so i Google the issue and found it was a random misreading and suggested to change the coil pack. however there is a found and rear coil.. how can i find out which cylinder is misfiring so that i can changed the correct coil pack.. or should i just change both to be on the safe said... has anyone had to do this. please share you thoughts..

Thanks

 

u need to get the vehicle scan and figure out which cylinder is missing

then u need to check the plug and wire to make sure they r working