2007 mazda 3i cylinder 2 miss fire P0302
 

So from the day I purchased the car new until now I have not had any real issues with my car. I drive 80 miles round trip everyday for work, Monday on my way in I took my exit off the interstate and stopped for a red light. Upon stopping the engine started idling poorly and check engine light came on. The next day I had the code read and it was P0302 cylinder 2 miss fire. I have purchased a new coil pack but would like to further investigate if it could potentially be another issue. The car has 130k miles and I replaced the plugs about 15k miles ago. I am considering pulling the injectors and see if I can clean them up. Has anyone else had this same problem? What was the solution?

Alright, tore the injectors out and cleaned them. Still no good. two codes pop up now "p0300 and p0302". Upon browsing these forum posts for the past 2 hours I have read anything and everything that could cause this code. Dirty EGR, crank sensor wire has fray, O2 sensors or pre cat. Any advice on where to start would be very very helpful.

Update as of now. clean injectors, brand new NJK's new coil pack on #2 seafoamed the crankcase ( valve had a slight tap to it thought possibility of it causing a problem with compression, and also checked the O2 sensors. New lower O-rings for injectors come in tomorrow so I can replace all the seals on them. next step is to clean EGR and possibly the throttle body. Does anyone know if taking the throttle body off will cause any resetting on it? It is electric so not sure if removal will throw a code on it. I see that some people talk about a bad engine mount, mine isn't leaking so I am not certain if it is bad or not.

Final update. Was finally able to do a compression test and had 90's across the board except for #2, it was 50. drop some oil down #2 and ran it again and sure enough bumped it right up to 90. It sadly was in the back of my mind the past few days. Considering a clegg engine kit since I have access to a machine shop.

You've been busy...
the P0300 is a random misfire, since that was after you pulled the injectors, maybe there's dirt in the fuel lines that is clogging the injectors every once in a while.
Has this car ever had the fuel filter changed, possible that it could be damaged or clogged causing problems.
The throttle body shouldn't throw a code unless it was unplugged with the ignition on. And I don't think there's any calibration or other issue if it's pulled off / unplugged.

The last note about compression is what sounds like the key. If cylinder 2 had half the compression of the others, and that was the first misfire - see what the problem on that is. The other codes could be red herrings.

No other codes anymore, one of the O rings on a fuel injector got damaged and I had to replace it. only code now is P0302 it is the rings in cylinder 2. I am looking at an engine kit from clegg engines and will be doing the rebuild myself august after I get all the components. Until then I put in a can of engine restore and am running 10w 30 rather than 5w-20 hopefully a little thicker oil will make the problem seem a little less until then.