Vacuum Port on Intake Manifold is open

[bcrooms]

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

 

[txab]

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

Edited March 12, 2018 by txab

[bcrooms]

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]

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

 

 

Edited March 12, 2018 by txab

[tbarn]

Is there vacuum at the port while running?

BTW P0455 is not vacuum related.

[bcrooms]

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]

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]

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]

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.

[Jose1993]

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 November 21, 2019 by Jose1993

[Ianf]

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 .

 

 

[rockford86]

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

 

 

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

 

[Ianf]

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

[txab]

12 hours ago, Ianf said:

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

Correct. Easily found at any parts store