So two weeks ago I got a CEL when I started up my car, P0302. The car didn't feel any different or anything. A couple days later I felt the stuttering and checked and the it had the code twice. Swapped the plug and it seemed to help resolve the stuttering but the CEL stayed on. Now a week later I'm getting p0300/p0304/p0303 codes along with the original.

Seems odd that all the plugs would go bad. I'm doing a seafoam now. I'm guessing next step is to swap all the plugs/ignition coils? I honestly don't have the cash to run it to the dealers and drop over 1k on it just to get it looked at and it's out of warrenty now, 48k miles. Any other suggestions? Thanks!

 

Did you figure this out? My car just did the same. I replaced plugs, but it's still throwing codes and has a lumpy idle.

 

I did the seafoam and its running a lot better without the studders but the codes are still there. My code reader can't clear them. I need to find someone in the Cincy area that can clear before I can say it's fixed

 

I'm sea foaming my car currently. Stay in touch though, as our cars have similar problems and mileage. I might look into media blasting mine this weekend.

 

After getting some gas last weekend I felt the idle was off and it was more unstable and jittery. Then this past weekend I noticed the check engine light was on, I was still running the same gas and had only used about 1/4 tank. I stopped by the dealer and asked what they thought and if they could do a quick code scan but was told I'd have to make an appointment and pay $500 for a diagnostic. Ouch! I decided to add a bottle of STP gas treatment and ran some errands and the light stayed on but the idle kept getting better. I ordered a ScanGauge II from Amazon with it being delivered today. I drove it to work (20 miles) this morning and the light stayed on although the idle felt better. When I started it up to drive home the check engine light was off and when I got home my ScanGauge was here so I checked the stored codes and sure enough they were the same as yours; 300, 301, 302, 303, and 304. I went ahead and cleared them and so far the light is still off. In my case it appears I had a bad batch of gas, maybe some water with the STP taking care of the problem. Fingers crossed!
My car has 36k miles and the only major maintenance it's had was the timing chain/tensioner replacement two years ago.

 

My CEL never went away, but I'm only getting a p0302 now when I do my scans. I'm going to swap coils around tomorrow and see if the code moves with it.