What is this connection? (top front of Intake Manifold)

[SB_Pete]

(2006 Trailblazer LT 4.2L 4X4)
Backstory - Recently had a P0171 and P0306 and couldn't pass inspection. I changed the air filter, cleaned the Throttle Body (Carb Cleaner), the MAF and MAP (MAF Cleaner - 12hrs + dry time), changed the Intake manifold gaskets and cleaned out the manifold, injectors, and head side of the manifold (Carb Cleaner). I'm now getting a P0106 and a P0171. I'm getting a very rough idle with the engine just dying as well. I have also tried changing the MAP sensor and giving the battery more than an hour disconnected. I am wondering if I forgot to hook something up here. What is this nipple?


I am hearing a whistling/sucking noise from this nozzle as well as this little cut out in the throttle body to intake manifold connection


If I block them with my finger, there is significant suction against my finger and the MAP sensor reading goes from ~21 inHg down to ~16 inHg.
Did I forget to hook something up here. I can't find any hose that would connect to it and I don't remember disconnecting anything there.

For reference I have OBDLink MX with which I can read codes and PID values. I am definitely more of a shade tree mechanic though - I bought this reader to troubleshoot this problem and am coming up empty. Any ideas?

Thanks in advance all,
-Pete

 

[djthumper]

We need some vehicle information to go with it. The top photo should have a cap on it, at least on my 06 it does. They did some changes between a couple of years.

 

[SB_Pete]

ah, you're right, I put that stuff into my profile but it's not showing up. Thanks for the head's up - I'll have to look into that. In the meantime
2006 Trailblazer LT 4.2L 4x4

 

[Ziggy]

Here's a pic of my 2002. There is a cap.

Not sure what you're looking at up near the throttle body, though. If it's got a vacuum leak up there too, I'd take it back apart and figure out why the throttle body isn't seated properly.

 

[SB_Pete]

Got it. Thanks Ziggy. Now that I see it, I remember not knowing what to do with that damn little thing. I didn't take it off, but prob knocked it off when I took off the resonator and didn't know what it is. I put a generic cap over that nipple now and that has fixed the idle quite a bit. Now showing ~14-16inHg, but still throwing a P0106.
The other thing I'm talking about is at the 12'oclock position on the throttle body, there is a little rectangular cut out (like 1mm little) on the intake manifold to receive a tab on the throttle body. There seems to be a vacuum leak there as well. I'll try dissassembly and reassembly and drive it around some more...

 

[Ziggy]

Got it. Thanks Ziggy. Now that I see it, I remember not knowing what to do with that damn little thing. I didn't take it off, but prob knocked it off when I took off the resonator and didn't know what it is. I put a generic cap over that nipple now and that has fixed the idle quite a bit. Now showing ~14-16inHg, but still throwing a P0106.
The other thing I'm talking about is at the 12'oclock position on the throttle body, there is a little rectangular cut out (like 1mm little) on the intake manifold to receive a tab on the throttle body. There seems to be a vacuum leak there as well. I'll try dissassembly and reassembly and drive it around some more...

Just went back to my truck to see if I can see what you're talking about. It would seem that you're missing the throttle body to intake manifold gasket. That little slot appears to be a positive locator for the rubberized gasket to make sure that the aluminum throttle body mates securely to the plastic intake manifold. Mine has a little spongy type rubber tab sticking up through the slot in the manifold. The P0106 code is a Manifold Absolute Pressure code. if you're missing the gasket, or the gasket is damaged or not properly aligned, basically what's happening is the engine is sucking unmetered air, downstream of the throttle body, causing the air/fuel mixture to go way lean. The computer is seeing funky stuff, and trying to accommodate for it, but no matter what it does, it can't overcome that massive (relatively speaking of course) hole in the intake stream.

 

[paulcmartin]

Should just be capped off. It doesn't connect to anything.

 

[mrrsm]

But to address the reasons WHY you failed the inspection...more than likely you had excessively high CO (Carbon Monoxide) and/or NDS (Nitrogen Di-Sulphide) readings due to one or all Four of these possible problems:

Upstream O2 Sensor is Bad
Downstream O2 Sensor is Bad
BOTH O2 Sensors are BAD
Catalytic Converter is CLOGGED and therefore... NFG

 

[djthumper]

Or false readings at the sensors due to a vacuum leak and excessive air into the TB.

 

[Mooseman]

Just for everybody's info, that nipple at the top pic is for EXT versions and the vacuum actuator for the rear heater water valve. For non EXT, some have a cap, some don't and it's closed internally. If you're feeling vacuum, you need a cap.

 

[SB_Pete]

"It would seem that you're missing the throttle body to intake manifold gasket."
Yep, Thanks Ziggy. I totally forgot to put the frickin gasket back in lol.
Problem solved. code P0106 went away and MAP sensor reading back down to ~11-12 inHg at idle.
(combined with capping that nipple also)

But to address the reasons WHY you failed the inspection...more than likely you had excessively high CO (Carbon Monoxide) and/or NDS (Nitrogen Di-Sulphide) readings due to one or all Four of these possible problems:

Upstream O2 Sensor is Bad
Downstream O2 Sensor is Bad
BOTH O2 Sensors are BAD
Catalytic Converter is CLOGGED and therefore... NFG

Just to clarify MRRSM, I didn't actually fail inspection yet, I haven't taken it yet because the SES light was on and I couldn't get it to stop throwing codes. Should be good to go now.
I replaced the Upstream O2 sensor as part of the general tuneup I was doing so that should be good to go. We'll see what the Inspection station says on the tailpipe sensor tomorrow, but at least I can actually get it inspected now lol.
Thanks guys.
-Pete

Or false readings at the sensors due to a vacuum leak and excessive air into the TB.

Yeah, that was what was causing the P0106 combined with intermittent P0171. MAP Sensor was reading ~21inHg at idle with the nipple uncapped and the gasket off - Engine could barely idle and was dying. Nipple brought it down to ~16 with a rough idle and a P0106 but no P0171, gasket brought it down to ~11-12 inHg. No more codes.

 

[Chickenhawk]

Does your code reader show any pending emissions tests? There are a few that require than than a couple of start/stop cycles, and members have had problems when they correct a problem and then go for an emissions test within a few days. Some jurisdictions will fail you if you have any pending tests. (On my scanner, it is indicated by an orange light instead of a green light.) If all is green, no problem. If not, you may have to drive it another day or two.

 

[SB_Pete]

Does your code reader show any pending emissions tests? ....

Yes, actually it did. I did not have a code reader before all this and bought an OBDLink MX specifically to track down my issue after the O2 sensor did not fix my SES light. It's actually a pretty cool little reader tool and has a function that shows all of the pending tests and when they are complete. It will even tell you when the car is ready for testing based on a drop down menu that shows multiple options for all 50 states (in my case "NC 2001-newer").

In any case, I waited until it showed all parameters ready for testing this morning and had it tested then renewed registration at lunch today.

Thanks for the heads up though - it is a very valid point.
-Pete

 

[Mooseman]

Took out the "Need help" since help is no longer needed

 

[SB_Pete]

Thanks Mooseman