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Vacuum Port on Intake Manifold is open

bcrooms
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bcrooms Enthusiast

bcrooms

Posted
Posted

So I just happen to notice there is a vacuum port on the passenger side of the intake manifold that is not connected to anything or plugged.

 

Is this port supposed to be left open or should it be capped with something? I ran a DIY smoke test on my 5.3 to further investigate a CEL relative to large vacuum leak.

 

Similar to the picture below. The one pictured below appears to have a rubber cap.  Mine does not.

 

Thanks,

Brandon

 

removing-intake-manifold.jpg

txab Senior Enthusiast

txab

Posted
Posted (edited)

It should be capped. It is it is unmetered airflow the ECM cannot take  read, thus it is a vacuum leak

Edited by txab
bcrooms Enthusiast

bcrooms

Posted
  • Author
Posted
34 minutes ago, txab said:

It should be capped. It is it is unmetered airflow the ECM cannot take  read, thus it is a vacuum leak

Thanks, someone must have missed this before I owned the truck. It's had code P0455 which I know can be related to other things, but I figured this could be the issue also.

txab Senior Enthusiast

txab

Posted
Posted (edited)

From the factory it doesn't really have "cap" like most would think. The "cap" is made as part of the injection molded intake. It can be broken off to open the port if necessary. If you can plug it and your leak goes away you've found your issue

 

 

intake.jpg

Edited by txab
tbarn Senior Enthusiast

tbarn

Posted
Posted

Is there vacuum at the port while running?

BTW P0455 is not vacuum related.

bcrooms Enthusiast

bcrooms

Posted
  • Author
Posted
14 hours ago, tbarn said:

Is there vacuum at the port while running?

BTW P0455 is not vacuum related.

I've researched the P0455 code as much as I can.  I understand it to be the evap emission system.  does that not have vacuum?

I've seen guys smoke testing vacuum and diagnosing the P0455 code

tbarn Senior Enthusiast

tbarn

Posted
Posted

It is evap system related. However, it is a sealed evap system leak. The test looks for vacuum decay after sealing the system. Not engine vacuum related. You  should have a lean code if there is a vacuum leak at this spot such as p0171 or p0174.

bcrooms Enthusiast

bcrooms

Posted
  • Author
Posted
7 minutes ago, tbarn said:

It is evap system related. However, it is a sealed evap system leak. The test looks for vacuum decay after sealing the system. Not engine vacuum related. You  should have a lean code if there is a vacuum leak at this spot such as p0171 or p0174.

Thanks for clearing that up for me.  I'm a noob at this stuff.

 

Only code i have is the P0455.  Is there any particular way to test the emission evap system? Or should I just replace that part?

 

https://www.amazon.com/dp/B01D8VLULK/?coliid=I2LDZE7C9488QR&colid=2306JRB4EQXZK&psc=0&ref_=lv_ov_lig_dp_it

tbarn Senior Enthusiast

tbarn

Posted
Posted

90% of p0455 codes are either the vent valve or gas cap. Take your pick and start there. The other 10% could a LOT of other things.

  • Like 1
  • 1 year later...
Jose1993 New Member

Jose1993

Posted
Posted (edited)

It needs to be capped. Otherwise code p0171 and p0174 will appear. Lean condition Air leak. If is capped and you get the same codes! look for other air leaks like the manifold gasket is very common issue. Before you change anything I recommend doing a gas pressure test to eliminate a gas issue. Injectors could be bad as well but that’s the Worst case scenario. 

Edited by Jose1993
Ianf Enthusiast

Ianf

Posted
Posted

If your engine is an E85 capable, then that port being open may also upset the computers ethanol percentage calculation to compensate for more air and dump more fuel in the system at low RPMs. Your fuel mileage will drop a little like 10% and you will need to reset the ethanol percentage and fuel trims after capping the port with a Good bi-directional scanner or Tech II.

 

It probably got knocked off when someone had trouble putting the upper cover back on. I jnow that what happened to mine .

 

 

  • 1 year later...
rockford86 New Member

rockford86

Posted
Posted
On 3/12/2018 at 3:15 PM, txab said:

From the factory it doesn't really have "cap" like most would think. The "cap" is made as part of the injection molded intake. It can be broken off to open the port if necessary. If you can plug it and your leak goes away you've found your issue

 

 

intake.jpg

any solutions to seal that plugged port when "cap" is broken off and gone?

 

Ianf Enthusiast

Ianf

Posted
Posted

Any parts place should have rubber caps that fit that port. 

  • Like 1
txab Senior Enthusiast

txab

Posted
Posted
12 hours ago, Ianf said:

Any parts place should have rubber caps that fit that port. 

Correct. Easily found at any parts store

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