Misfire, help!/ P0304

Nascop5

Member
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2002 Mazda Protege5
I noticed the car has been idling weird ever since the temperatures have fallen here in the Bay Area, they have barely gone below freezing if at All. Today I'm puttering around town and the rough idle gets more and more aggressive, then finally every time I would accelerate the whole car would judder about. I connected the obd2 connector and got 2/3 codes, P0304, P0660/ had the code pending for a little. I check to make sure all the coil packs are properly connected, I was thinking it wouldn't be the spark plugs seeing as how I replaced them 12k miles ago. I inspected the spark plug on cylinder 4, to see that the whole bottom is completely black, I knew the car ran rich and all but I was unaware it would get that bad, I replaced it with the same size plug. I check the spark plug on cylinder one, its meh, so I changed it all in the end the other two plugs as well. I clear the codes, the car starts up fine, then bam starts juddering again. I check the codes again, this time it's just the misfire code.I don't know what I need to go for next, I'm hoping I don't have to do the fuel injectors, because it's going to be hell otherwise.
 
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Protege5
Get a spark tester and check for strong spark on that cylinder. The tester needs to have an adjustable gap, they're under 10 dollars.

Consider replacing the coils if they're old. They commonly fail in strange ways. Check the plug wires too.
 

Nascop5

Member
:
2002 Mazda Protege5
Took apart the entire fuel injection portion under the hood to make sure it wasn't the fuel injectors, I will see about it being the coil packs, because its certainly not the individual coils. However now I hear a hissing noise when the engine is running, any ideas?
 
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Protege5
Vacuum leak, might be from the injectors since you disturbed the seal. Shoot some brake or carb cleaner around, if you find an area that changes the idle speed when sprayed, you've found a leak.
 

Nascop5

Member
:
2002 Mazda Protege5
Fixed the issue, was the driver side coil pack, and the O rings for the fuel injectors, thanks for the recommendation.