Using Dashcommand I see misfire codes P0301 and P0304. I can run along the highway triggering the code reads randomly, sometimes the codes will show up, sometimes they don't. There's no check engine light. Just an occasional, barely perceptible stutter at idle.

I've already replaced the spark plugs, and tried swapping the coil from between cylinders 1 and 2. The code doesn't move.

Fuel pressure appears right (~1100 at idle, about ~1700 @ 2200 RPM), so I don't think it's the HPFP.

Any other ideas?

I'm certified pre-owned so I will take it in, but I like to be educated first.

 

Carbon build up maybe?
I am still fighting the same misfires on cylinders 1 and 2. Next is cleaning the intake valves.
Hope your dealer can fix it and please don´t forget to report back what they find.

 

P0301 here and P0304 here. Under the causes should give you some ideas. Let us know what they say.

 

I've decided it wait it out a bit. I'm not even sure if its not just a problem with the cheapo OBD2 module I have. From everything I've read, pending codes should either become stored codes and throw a CEL or delete themselves after a certain number of drive cycles. They shouldn't be appearing/disappearing in the same drive cycle multiple times.

I'm wondering if my OBD2 module isn't really clearing the codes. The car is behaving fine, so now that I've changed the plugs and gotten a fresh tank of fuel from a different station, I'm just going to wait a bit and see what happens.

 

If it's still under warranty it still might not be a bad idea to drop it off and see what they say. That way you know for certain there were no real issues.

 

Just an update...

I burned through two tanks of gas since the initial codes and change plugs as mentioned in the first post and the codes eventually stopped coming up. Not sure which of those was the fix, but it's obvious that my cheap ELM27 code reader and DashCommand weren't actually clearing the pending codes, so they had to fall off naturally.

 

Great you finally solved the issue