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03 Jetta 1.8t MKIV

733 views 4 replies 2 participants last post by  That1Jetta 
#1 ·
Alright so my Jetta is misfiring and throwing codes P0301 and P0303, so it's misfiring 2 cylinders. I can hear a hissing noise coming from my engine bay, like a vacuum leak noise, I'm not sure where the leak would be, I wish I could upload a video so you can hear it. Where could it be leaking from or what's the most common area. The noise is coming from the drivers side of the engine bay. The coilpacks and plugs were just changed so what else could it be. And if it were a vacuum leak where should I look first.

In the picture is the area where I hear the hissing noise.
 

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#2 ·
There's a lot of vacuum lines in that area, especially under the intake manifold. It's hard to tell, but is there a vacuum hose hooked up to the fuel pressure regulator?

A common issue with the 1.8t is the ignition coil harness cracking. If the harness is good, then it might be a fuel issue.
 
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