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I have a 2004 cayenne turbo and was recently noticing a rumbling in the car at idle. After ruling out motor mounts, I eventually had a CEL pop up as p0308 for cylinder 8 misfire and p0300 for multiple random misfires. I check durametric and found that I was getting misfires happening in cylinder 8 while the car was idling but when I would press the accelerator it did not seem to increase the misfire counter. I replaced the coils a few years ago and went ahead and check them all again and did not see anything wrong or cracks. I also change all the spark plugs at the same time. To rule out a coil, I moved the coil pack from cylinder 8 to 5. After all this, I started getting the cylinder 8 misfire code again. What should I be looking for next, fuel injector issue, bad wiring, compression problems in that cylinder. The valve cover gaskets were also replaced a few months ago for leaks. What does it point to that misfires seem mostly to occur with idling.

Edited by mbagge01
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46 minutes ago, mbagge01 said:

If it were to be a compression issue, would it result in an engine rebuild or are the other potential ways to fix it.

 

Sorry, but unless it is a loose spark plug - compression loss usually means major engine work.

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I agree with Loren. 

 

You asked if it was a fuel injector issue (I didn't realize the 2004 Cayenne Turbo was DFI but I checked and it looks like it is).  I have seen the exact codes you have caused due to a bad injector (and it was also at idle).

 

Different engine but it had two codes:

1) a P030300 - Cyl.3 Misfire Detected 

and

2) P030000 - Random/Multiple Cylinder Misfire Detected

 

Replacing the injector fixed the issue.  Not telling you to throw parts at it, just a FYI data point for you.

Edited by Silver_TT
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You probably pinched your intake gasket when putting the intake back on. 

With engine running put a rubber vacuum hose to your ear and place the other end around the intake area of #8.  I'll bet you hear a hissing sound.

gs.jpg

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On 3/20/2021 at 11:07 AM, Silver_TT said:

I agree with Loren. 

 

You asked if it was a fuel injector issue (I didn't realize the 2004 Cayenne Turbo was DFI but I checked and it looks like it is).  I have seen the exact codes you have caused due to a bad injector (and it was also at idle).

 

Different engine but it had two codes:

1) a P030300 - Cyl.3 Misfire Detected 

and

2) P030000 - Random/Multiple Cylinder Misfire Detected

 

Replacing the injector fixed the issue.  Not telling you to throw parts at it, just a FYI data point for you.

It is not DFI.

The 4.5 litre engines are port injected.

The 4.8 litre engines are Direct Fuel Injection.

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Thanks for the info!  Ya, wasn't sure, I had just navigated to Sunset Porsche's parts website and selected 2004 Cayenne Turbo.  I was surprised to see injectors, the fuel rails, etc when I was navigating through the engine and fuel components.  I always search by VIN when I have it instead since it eliminates the possibility of stuff like this.

 

The 4.8 litre was around 2008 right?  This is when I would have expected the introduction of DFI (or thereabouts), 2004 too early.  I know Porsche is ahead on technology and all 🙂  That's why I initially was saying I was surprised.

 

I do agree with Davesly, if this started happening since the intake was put back on I would make sure you don't have a leak like he/she showed above.  This would cause misfires mostly on the cylinder the leak is on (as your error code showed) but can also cause others to miss.  Hopefully it's something simple like this.

Edited by Silver_TT
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