P0302 after changing plugs and swapping coils (2011 Mazda CX-7)

[BadMechanic]

Problem: P0302 Vehicle: 2011 Mazda CX-7 Steps taken so far:

1. Replaced spark plugs
2. Swapped coil packs to see if the misfire would move to another cylinder
3. Added fuel treatment

The car had an extremely rough idle before the fuel treatment. Now the car has a very smooth idle post treatment (Seafoam + Techron).

The STFT is -5.5% idling and LTFT is 3.1%.

My theory is that there is a dirty injector or the misfire is due to the fuel system because the idle improved significantly after some fuel treatment which is not completely because I am still driving on the same tank I.e., I haven’t gone through all the fuel treatment.

The misfire is neither audible or physical, and I was very surprised for the code to come back after driving another for a day and a half.

 

[m626gt]

Injector Masters

Gas fuel injector test clean rebuild specialist serving the greater Portland Metro area. All 2 and 4 stroke gas injectors including Etec, Ficht and Optimax.

injectormasters.com

 

[edmaz]

Was the CEL on along with the code before you did the fuel treatment?
Did the code and CEL reset on their own, or did you clear the code?
Did the CEL come back on when the code was set again after the fuel treatment?