4.2L vacuum line diagram? (2024)

David11946

Original poster

Member

Apr 24, 2012
14
New York
  • Mar 3, 2013
  • #1

Iv'e been looking around for a vacuum line diagram for a 4.2L I6 and I can't seem to find one. Can someone let me know where to find one? I bought my TB used and I thought they came from the factory with a sticker somewhere under the hood (like the old models). My TB doesn't have it and I haven't seen one in the Haynes manual.

I have an open vacuum port on the intake manifold plastic cover at the front. It is in the same side as the air resonator. I only just noticed it while I was changing plugs and coils today. Would anyone know where that port is to be connected ( or the diagram would be great)?

Thanks for the info if you have it.

M

Mypetropig

Member

Dec 29, 2011
226
  • Mar 3, 2013
  • #2

You need to fill out your profile info so that we know what model year you have when we look at the thread. If yours is before 07, I think that's the year the went to the MAP sensor by the air cleaner, then you have two lines for vacuum off the resonator. One of the lines comes off the valve cover and attaches to the lower left of the resonator. Its for the crank case vent and is about a 1/2" in diameter. If its on the upper right then thats the fuel pressure regulator and is about 1/8" in diameter. Hope this helps.

J

jalmanza

Member

Feb 2, 2021
1
home
  • Feb 2, 2021
  • #4

David11946 said:

Iv'e been looking around for a vacuum line diagram for a 4.2L I6 and I can't seem to find one. Can someone let me know where to find one? I bought my TB used and I thought they came from the factory with a sticker somewhere under the hood (like the old models). My TB doesn't have it and I haven't seen one in the Haynes manual.

I have an open vacuum port on the intake manifold plastic cover at the front. It is in the same side as the air resonator. I only just noticed it while I was changing plugs and coils today. Would anyone know where that port is to be connected ( or the diagram would be great)?

Thanks for the info if you have it.

did ou ever find out where the vacuum lines attach?
.

Mooseman

Moderator

Dec 4, 2011
25,608
Ottawa, ON
  • Feb 3, 2021
  • #5

If you're talking about that nipple on the driver side of the resonator, it connects to the fuel pressure regulator as per this image:

4.2L vacuum line diagram? (5)

Or do you mean the one on the intake?

4.2L vacuum line diagram? (6)

That one connects to the vacuum line that goes to the rear heater coolant diverter valve on EXT's only. SWB trucks are plugged with nothing connected. Seeing yours in an EXT, you should have it. It's a plastic line that runs from the back to the front of the valve cover.

What's this hose? (Long Wheel Base)

Last weekend, while helping a buddy change spark plugs on his mom's EXT, I noticed this small hose was broken. It connects to the intake manifold, runs back along the coil packs, then heads over to the passenger side somewhere. Couldn't quite see what it connects to, but there's a junction so...

4.2L vacuum line diagram? (7)gmtnation.com

walt45806

Member

Mar 22, 2021
2
Lima, Ohio
  • Jun 28, 2021
  • #6

so that should be plugged on my LS??

walt45806

Member

Mar 22, 2021
2
Lima, Ohio
  • Jun 28, 2021
  • #7

So this Vacuum Port on the intake manifold should be capped on my 02 LS?

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TJBaker57

Member

Aug 16, 2015
2,954
Colorado
  • Jun 28, 2021
  • #8

walt45806 said:

So this Vacuum Port on the intake manifold should be capped on my 02 LS?

Here's some higher detailed pics of my 2002 LT....

  • 4.2L vacuum line diagram? (15)

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Member

Oct 22, 2015
7,954
Tampa Bay Area
  • Jun 28, 2021
  • #9

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TequilaWarrior

Member

Dec 5, 2011
578
Central Pennsylvania
  • Jun 29, 2021
  • #10

walt45806 said:

So this Vacuum Port on the intake manifold should be capped on my 02 LS?

It is most likely that the port you are referring to goes nowhere. It is likely plugged on the inside - if it weren't it would emit a sucking noise constantly. If you put your finger to it and feel vacuum, then YES you need to plug it. My '02 Bravada had a rubber cap on the end of this and it disintegrated over the years. It is plugged on the inside but I placed a new cap on it anyway.

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4.2L vacuum line diagram? (2024)
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