It's probably been covered somewhere I'm just missing i.
Car died jump started it, ran for two days cool. Ses light came on right after I punched it to get out of traffic. Car felt like it was missing, intermittently when it runs good SES light goes off. (I can fill the car shutter and the light start to blink). I thought it was a voltage problem not getting enough spark or some pooh. Put a obd scanned came up with (P0420 and P0301) thought to myself alright I need a new battery anyway let's start there. New battery in next misfire issue changed plug in cylinder 1, cleared codes. Drove it about 3 miles coming off the Fwy I felt that misfire again and the car is stumbling (it doesn't shut off though ). Scan says misfire #1 P0301.Now switch coil packs #1 with #3 and vice versa, clear codes and drive (3 miles driving and light goes on,vehicle stumbling). Scan tool now shows code P0303 BINGO bad coil pack right process of elimination right. (50 bucks new coil pack ready to go juiced up)! Slap it on number 1 cylinder and return number 3 coil pack to original cylinder clear codes and high on life. I even detail the inside cause she is now purring. Wife takes it to work about 15 miles away,she calls (babe car runs great ). Yeah I'm the man lol.
On her way home though, different story. Car starts to stumble, here I am lost missing something.
Codes read
P0301
P0420
P0733
(I no longer have a pre cat hollowed that dog out)

Well to start off what is the year make and model of the car and if it has an engine swap what motor is in it?