Hello, so I have minor knowledge about vehicles and I started having a misfire in my 03 g35 sedan. there's an oil leak issue that hasn't been taken care of because i cant afford a mechanic and i dont have an engine hoist (unsure if relevant to my issue) . I got codes for a cylinder 4 misfire and the 02 sensor code recently and p1148 manufacturer control. So i decided to change the spark plug and now it backfires while idling or in low RPMS if not moving, a mechanic suggested to test and switch coils with another cylinder it now is misfiring in cylinder 4 and cylinder 2 and barely holds an idle and struggles to start. the 02 sensor code and the misfire code expanded to both banks/cylinders. should I get a set of ignition coils, new 02 sensor, fuel injector or even something else entirely?

 

Sounds like you got the coil pack harnesses mixed up when you were plugging everything back in.

Let me dig up a post where I listed what color wire goes to each cylinder.

 

Check out this post, each coil pack has two wires, one of them is different on each coil pack.

Cylinder 1 is the right front (passenger front) and that bank has 1, 3, 5.

Cylinder 2 is the left front (driver front, and that bank has 2, 4, 6

https://g35driver.com/forums/g35-sed...ml#post7207226

 

If they're plugged in correctly then clear codes and start the car again. It's probably still remembering the code from last time but you might have a bad coil pack which ended up on a different cylinder so now it has both sets of codes stores.

See which cylinder code pops up, remove that coil pack and thoroughly inspect it for some obvious damage, blistering of the expoxy resin encapsulation (black shiny part at the top), scorching of the well tube boot, corrosion of the contact spring inside the well tube boot. You can pull the well tube boot off to inspect better, also make sure the harness contact pins aren't bent or corroded and that the harness locks into place properly.

If it does still throw codes post all of them here.

 

bought a pair of new coil packs, no more backfiring thankfully its running a thousand times better than it did this morning, I do still have a code pop up for an 02 sensor and a cylinder 2 misfire even though that one wasn't messed with

 

Since you're having multiple coil pack failures there's a high likelihood that the ignition condenser is failing. Fortunately it's super cheap and only about $15 and easy to replace. It plugs into the coil pack harness on the right side of the engine bay between coil packs 3 and 5.

Nissan part number 28351-89902