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Discussion Starter #1
So I have been having a very annoying issue with P0304.
I have swapped plugs, coil packs, injectors, have new cams, lifters & rockers.
I have done a leak down and compression test and everything is normal.

If I start the engine and put it in gear quickly, it doesn't throw the code.
It only seems to throw the code when it idles at start up.
I noticed the other day, it's idling around 650 - never above 700.

What is the idle supposed to be and does anybody have any other input of what to look for?

Thanks in advance!
 

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“An EGR valve that is stuck open, a leaking Intake Manifold Gasket, a defective Mass Air Flow Sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire.”

Since it only happens at cold idle, a lean misfire sounds like a possibility. Above are some possible causes.


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(Pentastar has no EGR and no MAF)

Do you have access to a good scan tool? Does your scanner show how many misfires? Do you feel it missing, or is it just a code? And then is it always and only P0304, so cylinder 4 misfire?

Also you say it happens after startup, though you have to mean RE-start-up with warm engine. Otherwise if the engine is running cold, then it should be running in open-loop and no misfire code should be set (at least according to the pre-canbus vehicles that I have been working on).
 
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