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2006 Altima 2.5 S misfire P0304

posted May 27, 2016 01:57:35 by juan campos
Hopefully someone can shed some light on what my issue is. I have an intermittent misfire only when I start the car when the engine is cold. You can feel the misfire when I start the engine but only lasts a few seconds. The car runs perfectly fine after. The only issue is the slight shaking when car is started. Swapped coils and spark plugs and code is still P0304. Any suggestions on what the issue might be?
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7 replies
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RassielCotoMedina said May 27, 2016 11:43:54
check fuel pressure and if it holds, that could be a leaking injector, i remember having this condition on a grand caravan and it turned out to be a head gasket faluire, so rule out the injector and then you can move on, posible causes that i can think of:

- Leaking injector
- Head Hasket Faluire
- Vacuum leak only when cold (not so sure about this one cause the condition according to your description last for a few seconds)
- Low compression

Hope this helps.
[Last edited May 27, 2016 11:44:50]
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AndyMacFadyen said May 27, 2016 13:01:10
To the above list add a sticking valve.
I also have seen seen cases where a head gasket failure or an inlet manifold coolant leak caused these symptoms. In both cases coolant was only leaking back into the cylinder when the engine was cold. You might find it if you stop the engine immediately afer it starts from cold and looked for traces of water on the spark plug and in the cylinder. You could also try a cylinder leak down test on a cold engine looking for bubbles in the coolant or a cold pressure test on the cooling system.
"Rust never sleeps"
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juan campos said May 27, 2016 18:13:53
Thanks for the suggestions. I just removed the spark plugs and cylinder 4 has some small amount of oil? coolant? at the very bottom of the spark plug well as it gives a reflection when using a flashlight. The spark plug itself in cylinder 4 is dry and no oil/coolant on it. This is telling me I might need to replace the head gasket?
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Tyler said May 28, 2016 14:39:15
If you're seeing oil at the bottom of the spark plug tube, then that simply indicates a leaking valve cover gasket, not necessarily a head gasket issue.

I think Andy and Rassiel are right on in their suspicions. Andy's suggestion of using a cylinder leak down test and looking for bubbles in the coolant would be my next move.
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cheryl hartkorn said May 28, 2016 14:55:55
try smoking the intake when its cold. see if you have a leak. if not possible injector issue.
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juan campos said May 29, 2016 03:04:22
The oil is in the combustion chamber not sure how a leaky valve cover gasket can be the culprit but then again I'm a shade tree mechanic. Did more digging and i might be worn valve stem seals. Going to start using 10w 40 oil in hopes that the thicker oil can control the issue as it's minor at this point.
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MattWhite said May 31, 2016 15:24:13
I can understand Tyler's comment. You said it was wet on the plug but dry at the bottom. Does the engine use coolant at all?

Personally I'd pressure test the cooling system overnight and see how it is when you start it. My gut feeling is if there was enough oil in there to make it misfire it'd be belchimg smoke. The other suggestion already mentioned is monitor fuel pressure drop over a period of time.
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