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P0304 Engine Code

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Old 12-11-2018, 07:09 PM
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Originally Posted by hurst2001


thanks for explanation I’m asking is the same as the 2.2 or 2.4 motor the same ?
I am not completely sure about the 2.2 or 2.4, since I have no experience with anything but the 2.0 turbo. I'm going to guess that the 2.2 or 2.4 may also experience the same problem because I believe it has at least one of the same PCV paths via the hidden PCV valve in the intake manifold. And it's also direct injection. So my guess is that it too could have valve coking. Perhaps someone else with more 2.2/2.4 experience in this thread may chime in.
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Old 12-11-2018, 08:54 PM
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Originally Posted by m_ridzon
I am not completely sure about the 2.2 or 2.4, since I have no experience with anything but the 2.0 turbo. I'm going to guess that the 2.2 or 2.4 may also experience the same problem because I believe it has at least one of the same PCV paths via the hidden PCV valve in the intake manifold. And it's also direct injection. So my guess is that it too could have valve coking. Perhaps someone else with more 2.2/2.4 experience in this thread may chime in.
thank you !! Well we will see if anybody got any info on this ..
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Old 12-11-2018, 09:31 PM
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FYI. The 2.2 and 2.4 are not Direct Injection.
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Old 12-12-2018, 07:02 AM
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Originally Posted by firemangeorge
FYI. The 2.2 and 2.4 are not Direct Injection.
Hmm, learned something new. Poking around Google, I thought for sure I saw 2.2/2.4 engine images with the fuel rail tucked under the intake. Perhaps I misinterpreted the sites I was looking at though. Nevertheless, @hurst2001, the fact that they are not direct injection basically clears them of the issue. That is, the valves will experience "fuel wash," which means they are far less likely to coke.
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Old 12-12-2018, 09:39 AM
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Old 12-12-2018, 09:55 AM
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Originally Posted by Oldblue
I'm confused. @firemangeorge previously said the 2.2/2.4 were NOT direct injection. Therefore, I would assume the intake airstream would have fuel in it to "wash" the valves. Thus, why would a catch-can be needed on those engines? I understand that the catch-can separates the oil out of the airstream, but is it really needed if the engine is not direct injection?
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Old 12-12-2018, 10:00 AM
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Originally Posted by m_ridzon
I'm confused. @firemangeorge previously said the 2.2/2.4 were NOT direct injection. Therefore, I would assume the intake airstream would have fuel in it to "wash" the valves. Thus, why would a catch-can be needed on those engines? I understand that the catch-can separates the oil out of the airstream, but is it really needed if the engine is not direct injection?
Short answer, yes. The PCV system still contaminates the air inlet on the others, the PFI washes the contaminants/oil mist off the valves
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Old 12-12-2018, 10:07 AM
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Originally Posted by DrLoch
The PCV system still contaminates the air inlet on the others, the PFI washes the contaminants/oil mist off the valves
Yes, I understand that contamination still occurs. But for as long as engine designers have incorporated PCV airstreams on the engines (decades), the issue never really caused much grief. My understanding is that it only became a real issue with the advent of direct injection.

Nevertheless, I suppose I can agree that a cleaner intake airstream is always preferred over the oil contamination, regardless. So I suppose putting a catch-can on certainly wouldn't harm anything.
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Old 12-12-2018, 10:14 AM
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As DrLoch stated, the PCV air on the 2.2, 2.4 enters the intake before the fuel injectors. Dirty air can contaminate the TB and intake runners before it gets where the fuel can clean it.


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Old 12-12-2018, 12:27 PM
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Yes, the oil gets sucked out of the valve cover, then gravity let’s the oil run down to the elbow at the throttle body, resulting in oil being pooled in the bottom of the intake manifold.
I tried the loop hose in FMG’s picture but still the same problem, there is no PCV valve, just the vacuum of the intake manifold.



This is the factory PCV hose, straight out of the valve cover, no PVC valve

As you see here, there is a feeble attempt to use gravity to let the oil flow back into the valve cover.


This is thread in #8 Dowbrew has an explanation of the SS PVC valve and hose routing

https://www.chevyhhr.net/forums/ss-s...-hhr-ss-47584/

and better pictures in here

https://www.chevyhhr.net/forums/2-0l...tch-can-54350/
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