New project car 5.4 V12

[Javier96]

So I just bought a 1995 750il with about 210k miles on it. It does have some issues i get code p0300 and a few other misfire codes. The previous owner said he replaced all the spark plugs and that didn't do it. He then said he suspected a vacuum leak. I don't know where to begin as far as how or where to look for said vacuum leaks. Any help would be greatly appreciated. Thank You!

[asianvenom]

How about distributor caps and rotors? If you look at rough running with inpa or a code reader that able to read stft and ltft, you can determine if it is vacuum leak or not

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[Javier96]

I don't think its the caps and rotors i do hear a hissing sound coming from the back of the engine. Could it be the intake manifold gaskets if so how could i confirm that?

[asianvenom]

I don't think its the caps and rotors i do hear a hissing sound coming from the back of the engine. Could it be the intake manifold gaskets if so how could i confirm that?

There you go...! Sound like a busted pcv, there is one on each side, put your palm on the back of manifold see if stops the hissing.

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[Javier96]

So i did that and it did make it go away i took it off and there is oil on it is that normal?

[asianvenom]

Replace them, you got a major vacuum leak, that's why you're getting misfire

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[Javier96]

they are the major vacuum leak?

[asianvenom]

Yes, you did feel/hear that vacuum leak with your palm didn't you?

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[Javier96]

Yes i did when i put my hand behind it the hissing would go away

[Javier96]

So its supposed to have oil on the inside of it right? or is that a different issue?

[Javier96]

So I just got them in going to replace them and see how that goes will keep you guys updated