Misfire Confusion

[Mr.RMFC]

Ok, so ive read a bunch of the different misfire threads but could not find one that matched with what im seeing.

 

So I am getting a cylinder 3 misfire (I have an accesport to read the code) with the rough idle. This only happens when at idle or low speed as I can clear the code and drive on the highway if needed. It does have the flashing cruise light so I drive it as little as possible as I have a diagnosis scheduled at a shop.

 

What I have done so far.

1. Replaced coil pack

2. Swapped injectors with cylinder 1

3. Cleaned the spark plug when it was out (Did not seem fouled)

4. Ran Seafoam through the fuel

5. Ran Octane Booster through the system

 

What I found interesting was that, when I ran the seafoam through the system, it seemed to help for about 2 hours of normal driving as it made the idle a lot smoother and super small misfires a lot farther apart. after that 2 hours, it returned to normal roughness and threw the code.

A similar thing happened with the Octane Booster but it went smoother than the seafoam but for a shorter amount of time.

I have also run fuel from different stations to experiment with that with basically no difference.

 

I have it scheduled at the local dealership as no one local can do a full diagnosis (nearest "Subaru" performance shop is 176 miles away)

Figured I would post on here to see what people are thinking

 

side note: The SeaFoam really reduced the valve noise which was nice

[relative4]

Have you swapped the spark plug with cylinder 1?

 

A worn coil pack connector is a possibility. A tiny twist on the pins with needle-nose pliers may help.

 

Compression test is next.

[moral hazard]

Have you checked for a vac leak?