Engine misfire but not code

Is there a trick to know if a ignition coil is causing a misfire? My car is misfiring but not throwing a code.
I don’t want to unplug while running because I’ve heard it could do some damage.

If there’s no misfire code, there’s no misfire.


Yea I figured; was hoping it was simply a misfire. The car exhaust is releasing white smoke and hope it isn’t a head gasket. So could a head gasket cause the engine to run rough or misfire


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:frowning: I guess it’s time to replace a head gasket

What year and model is your Mazda?

Tester nailed it.

Diagnose first, replace if that diagnosis shows a head gasket. There are products that can test for head gasket leaks. Like this:


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It’s much worse; I’ve checked the spark plugs and they have oil in them(just a little not soaking)and I checked the air filter and it has a lot of oil on it; now i think it’s the piston rings

Have you checked if the PCV system is restricted?


No, I’ll check right now

How do I check that? Do I just check the pcv valve

Oil on the spark plug tips? That could be good news, at least in relationship to the head gasket fault theory. When coolant leaks into the cylinders via a faulty head gasket, that often steam cleans the spark plugs. Some white smoke out the tailpipe is normal, especially in the first 5-10 minutes after starting a cold engine, & even longer when the ambient temperature is cooler than normal.

There’s a few fairly easy owner-checks for a possible head gasket fault

  • the engine will be losing quite a bit of coolant, cup a week or more, but no leaks under the parked car
  • the amount of white smoke from the tailpipe w/ warm engine will dramatically increase when rapidly accelerating, like on a freeway on-ramp
  • there will often be visible bubbles coming to the top of the radiator (radiator cap removed) as engine idles, more so when increasing the idle rpm.

I’ve checked the pcv and it rattles so I think it is the piston rings

Time to run a compression test.

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