New Project Car Misfiring

[Whiplash]

Hi everyone.
About a month ago I purchased a very high mileage, rough interior, rough exterior but excellent running 2010 4.6L Genesis.
It's been sitting since and I have turned it on twice a week just to keep battery proper.
About 2 weeks ago when I turned it on the engine started misfiring right away. It now does it every time I turn it on.

I'm getting the following CEL codes:
P0300 - Powertrain, Random/Multiple Cylinder Misfire Detected
P0306 - Powertrain, Cylinder 6 Misfire Detected
P033D - Powertrain

I've searched the forum and haven't been able to find anyone with all 3 of these codes, but misfires seem to be common.
Can anyone shed any light on what the actual issue may be? Somewhere I should start?
Thanks.

 

[Qship]

I'm getting the following CEL codes:
P0300 - Powertrain, Random/Multiple Cylinder Misfire Detected
P0306 - Powertrain, Cylinder 6 Misfire Detected
P033D - Powertrain

I've searched the forum and haven't been able to find anyone with all 3 of these codes, but misfires seem to be common.
Can anyone shed any light on what the actual issue may be? Somewhere I should start?
Thanks.

Generally, start with the cheapest thing to do.
P0300 means there's more than one cylinder misfiring.
P0306 is obviously Cylinder 6 misfiring.
It could very well be that some plugs and some ignition coils are dead, or just plugs, or just coils.
As I suggested, start with the cheapest thing. vacuum lines, throttle body cleaning, maf sensor.
9 times out of 10 with misfire codes though, it's one or both of these: plugs and coils.
P033D is knock detection out of spec. I can't say I've ever dealt with this one before. Either the knock sensor is detecting an abnormally high knock (maybe bad gas? I mean REALLY bad gas). Or could be the knock sensor itself that's failing or the actual powertrain control module.

 

[Gunkk]

Fuel, air, compression and spark.

Try these:
1. Swap #6 injector with another cylinder, see if the problem moves. If it does: replace the bad injector.
2. Compression test #6. If low, then possible valve dropped (e.g. valve spring failed) or other hard mechanical failure like a lifter, etc.
3. Swap #6 coil with another cylinder, see if the problem moves. If it does: replace the bad coil.

 

[pmckechnie]

Whiplash, I would like to add to the above diagnostics you have gotten, both good. I think the first thing you need to do is put some fresh gas in it and drive it. Starting a car and not driving it is the worst thing you can do. Give it a chance to clean itself out.
If you will not be driving it for a while, just unhook the battery. When you get ready to drive it, recharge the battery if it is dead.

 

[Whiplash]

Thank for the help guys.
Next weekend I will check the coils and plugs. And update progress in here.

I hate to do this in the same thread, but does anyone know the part number or an easy method to put rear plates on the trunk? Right now the trunk has pretty large empty holes where the screws for the plates go. I think previous owner may have accidentally broke whatever was securing the screws to the trunk?

 

[Gunkk]

Probably best to talk to a body shop, but you can probably DIY as well with one of these:

https://www.amazon.com/Black-License-Plate-Screws-Fastener/dp/B07N4JLZYQ/

and some of this:

https://www.amazon.com/J-B-Weld-8237-PlasticWeld-Plastic/dp/B003S2E4UE/

 

[mike44138]

If I recall correctly that rear panel on the trunk is pretty easy to remove and get access to the back side.

 

[Whiplash]

I'll look into that as well if I need to. Hopefully those plastic inserts will do the trick. The holes do look blown out though. I already have some JB weld for plastic so I may use that with the plastic inserts.