[That1Jetta]

Okay so my 2003 VW Jetta 1.8t is making a hissing noise and throwing these codes as follows. Plugs were changed, coilpacks were changed, injectors were checked and they are fine, coilpack wiring is good. I don't know if it is a vacuum leak or what but I need to get this fixed ASAP.

P0300-Random/Multiple cylinder misfire
P0301-Cylinder 1 misfire
P0302-Cylinder 2 misfire
P0303-Cylinder 3 misfire
P0304-Cylinder 4 misfire
P0507-Idle Control System RPM Higher Than Expected
P0171-System too lean (Bank 1)

those are the codes it is throwing, I have a video of the car making the hissing noise, as well as another video with me spraying some starter fluid on some hoses and the car did idle up, If there is a vacuum leak I have no clue where it is, someone please help me. What hoses or connectors should I be looking at.

Also in most cases when a car is throwing multiple codes, fixing 1 thing can solve them correct?

Hissing Noise
https://m.youtube.com/watch?v=GXxEF3voCOA

Car Idle up with starter fluid
https://m.youtube.com/watch?v=YxLEl4tOI6c

 

[That1Jetta]

I would start by removing that bracket on the intake manifold which holds the N249 and the N112. There's a lot of vacuum lines in that area you're spraying, so it could be the ones under the intake manifold too.

I replaced all my vacuum lines because the factory stuff gets brittle and cracks over time.

The other option is to do a smoke test (Might need a shop to do this).

I think I found the leak, there is a hose under the intake manifold that I was moving around with a screwdriver and the hissing completely dissspeared and the cars idle went really smooth, but as soon as I let pressure off the hose the hissing is back, so I'm sure it's the hose I was playing with but it's really hard to get to because my bit ass manifold is in the way.

 

[That1Jetta]

If you remove that bracket on the front of the intake manifold (Should be 2 bolts), you can get more room to reach under the intake manifold.

Picture for reference.

Yeah but there are other hoses attached to the bottom of the bracket also the hose I'm touching with the screwdriver, is all the way under the mani

 

[That1Jetta]

I would start by removing that bracket on the intake manifold which holds the N249 and the N112. There's a lot of vacuum lines in that area you're spraying, so it could be the ones under the intake manifold too.

So there is like a T looking connector with hoses on it, I think that is the problem because when I push on it the car goes back to a Normal idle

The other option is to do a smoke test (Might need a shop to do this).