P0300 code on 06 Altima 2.5

Hi - any luck diagnosing the issue? I have the exact same problem on my 2006 2.5 Altima- even the sloshing water sound. I have both a P0300 and 303 code. I'm gonna change spark plugs and the coil on cylinder 3. I'm still not sure about the water sloshing sound.

I had that exact same issue! It's the head gasket from the sounds of it. I suggest to sell it or repair it before you continue driving it. Because the car will only get worse. The water sound when you accelerate or press the gas is the water from your radiator going to your engine. Try this: Fill the radiator full, leave the cap off and have someone else turn on the car, if water shoots out of the radiator you can be sure it's a head gasket issue

Don't waste money on new spark plugs, those things last years

An update for those interested: I took it out to the shop and the mechanic cleaned out the fuel injectors, changed the coil pack and replaced spark plugs. Problem still persisted. I took it back to the shop, they ran a pressure test and found water in two of the cylinders. So the problem is either a blown head gasket or a crack in the head. Since the car has over 150k miles on it, they suggested replacing the entire engine to be safe. I decided not to replace the engine and instead to essentially drive the car into the ground and just sell it for salvage when it happens. I've been driving it for about a month now with no real issues. The check engine light comes off and on periodically and I just have to put coolant in it every couple days. Hasn't died on me yet.

I had the same issues with my 06. Went to the grocery store, came out and wouldn’t start. Started researching and ended up here. What I did was replace the valve cover/gasket, ignition coils, and spark plugs. The bad gasket was leaking oil so badly and the seal that rests at the top of the spark plug cylinders leaked oil into the spark plugs which caused the misfire, which caused the car to not start. The part I bought was from 1aauto.com or something like that. The valve cover, gasket, and ignition coils were around $140. I was able to do the work myself which took like 30 min. The company I bought the part from even has a YouTube channel that tells you exactly how to do it. I happen to have a scan tool and I was getting code P0300 misfire. What’s kinda funny is I ordered the new valve cover before the car broke down and that’s exactly what it needed. I hope someone finds this info useful. I was stressed out thinking my car was dead for good. One easy way to tell if that’s the issue is to look around the valve cover and see if there’s oil. But also use a 10mm and take out the coils and see if they have oil on them. If so that’s the issue.