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Discussion Starter · #1 ·
I just got a 2012 Mazda 3 about a month ago and I’ve had nothing but problems with it. It keeps doing the “limp mode” thing and I’ve done everything I’ve seen on forums to fix it. I have a p0302 misfire on cylinder 2 and I’ve replaced coils plugs and gotten a new top of the line battery but nothing seems to fix it. Any ideas before I get rid of it?
 

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Did you get it checked before you bought it?
What codes were showing before you bought it and now?
Did you pull out the spark plug and inspect it?
Is the coil pack you replaced OEM or reputable brand?
 

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Could be an intake manifold leak. Pulls air in around the sensors and leans out the mixture. have you checked for vacuum leaks? How about a compression test? A misfire isn't necessarily an ignition problem. Could also be the cylinder 2 injector is partially plugged or not opening correctly.

Maybe if you describe all the symptoms. Just saying it's a misfire doesn't tell us much.
 

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2012 Mazda 3 GX MT5 non sky
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Like Zero G mentioned ... intake maniford leak , intake solenoids not working will mess with throttle and intake settings , dirty injectors (do a liqui moly fuel system cleaner), clogged fuel filter, when was last time the spark plugs were changed? . What codes are you showing only p0302?
Here is what i could find for p0302 mazda code :

  • Faulty spark plug 2
  • Clogged or faulty fuel injector 2
  • Faulty ignition coil 2
  • Fuel injector 2 harness is open or shorted
  • Fuel injector 2 circuit poor electrical connection
  • Ignition coil 2 harness is open or shorted
  • Ignition coil 2 circuit poor electrical connection
  • Insufficient cylinder 2 compression
  • Incorrect fuel pressure
  • Intake air leak
If it is compression issue , piston ring can be the issue or Value Stem seals (they do dry up is your maintenance is not regular) Liqui Moly makea a oil saver product to rejuvenate
high mileage engine seals (engine gasket , valve seals ...basically any seal the oil makes contact) .
Incorrect fuel pressure can also be caused by a faulty fuel pump or blocked fuel filter. If its faulty the code may not show right away causing a code to pop further down the line like
a lean A/F and cylinder misfire.
Connection to ignition coil could be faulty ... not all pins making contact
 
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2013 Mazda 3 i Hatchback
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The first thing is to stop throwing parts at it. Test and verify your cause before just trying things. As the others have said, the misfire could be from a host of causes, and you need to know what it is before you throw parts at guesses. The internet is full of good advice, but it's way easier for me to tell you that your problem is X than it is to ask you lots of questions for several days to get to the real answer.

A cylinder that isn't firing is missing one of the three components:
  1. Fuel. Is it getting too much, not enough, or none at all? Bad injector in #2 is the most likely in this category, as general fuel system problems (such as low fuel pressure) would show misfires on multiple cylinders.
  2. Spark. Is it actually getting good spark? You replaced the coil and the plug, but is it actually sparking? You can pull the plug and put it in the connected coil, laying the plug tip near grounded metal. Then pull the fuel pump fuse and crank the engine. you should see strong arcs from the plug to ground.
  3. Air. This one is the most broad. Is the cylinder getting all of the air it needs (but not extra), and is it getting compressed by the engine before ignition? An intake leak would have to be closer to #2 for the misfire to only be there, so perhaps a manifold gasket failure or cracked intake manifold runner. A smoke test of the intake system would be a good idea to look for leaks. You should also consider a compression test to verify that #2 is comparable to the other cylinders. Low compression could be caused by worn rings, blown head gasket, valve stem seals, worn valves, or other valvetrain damage.
Other information that would help us to figure this out includes: miles on the car, more history of the problem (as others have asked), what the old plug looked like (wet, burned, etc), compression test results, confirmation of spark, smoke test results, and if you have access to a OBD scanner with live data, any wierd results (such as fuel trims).
 

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Discussion Starter · #6 ·
After a long ass day of learning I pulled the plugs and saw that the misfiring cylinder was running lean. So I pulled the injectors and they were all super dirty but the the misfiring one was awful looking so I’m getting all four sent out to get cleaned (I would take them somewhere, but I live in the asscrack of West Virginia so there’s nowhere close). Thanks for the help guys I will keep you updated on the car when I get the injectors back. I was really on the edge of getting rid of this car but y’all convinced me to keep at it and find what’s wrong, and I learned a bunch on the way. So once again thank you everyone I really like this car and I’m glad I have hope to keep it for the first time in a couple months.
 

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I just got a 2012 Mazda 3 about a month ago and I’ve had nothing but problems with it. It keeps doing the “limp mode” thing and I’ve done everything I’ve seen on forums to fix it. I have a p0302 misfire on cylinder 2 and I’ve replaced coils plugs and gotten a new top of the line battery but nothing seems to fix it. Any ideas before I get rid of it?
I just got a 2012 1 week ago, how many miles on your x
3 ?
 

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Running better?
 
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