1998 yukon Mystery p0300 and rough idle still

[east302]

Meant to add, if you’re getting vacuum at that valve when the temperature dial is not on Max, then that valve will be closed and you’ll have no heat. Problem is either the solenoid or your a/c panel in that case.

 

[OilBurner2003]

Meant to add, if you’re getting vacuum at that valve when the temperature dial is not on Max, then that valve will be closed and you’ll have no heat. Problem is either the solenoid or your a/c panel in that case

I will add that to the list…Thank you sir! I swear, this truck.

 

[OilBurner2003]

Meant to add, if you’re getting vacuum at that valve when the temperature dial is not on Max, then that valve will be closed and you’ll have no heat. Problem is either the solenoid or your a/c panel in that case.

After a couple hours and completely snapping a vacuum line that was so brittle, I’m ready to take the intake out. Although, it’s not budging. I have everything out, bolts, valve covers, alternator bracket and AC compressor bracket, can’t get this thing to even move a bit.

Edit: Woo! I got the damned thing out. Here’s what it looks like, sure is some cloudy fluid down there…I don’t know much about what is supposed to go down there, but that looks kinda coolant mixing with oil slightly? I’m sure someone here will tell me what exactly happens. Here’s the condition of what it looks like:

 

[YukonGTmaster]

After a couple hours and completely snapping a vacuum line that was so brittle, I’m ready to take the intake out. Although, it’s not budging. I have everything out, bolts, valve covers, alternator bracket and AC compressor bracket, can’t get this thing to even move a bit.

Edit: Woo! I got the damned thing out. Here’s what it looks like, sure is some closely fluid down there…I don’t know much about what is supposed to go down there, but that looks kinda coolant mixing with oil slightly? I’m sure someone here will tell me what exactly happens. Here’s the condition of what it looks like:

How does the mating surface on the Lower Intake look around the coolant ports? Mine were Very pitted!

 

[OilBurner2003]

How does the mating surface on the Lower Intake look around the coolant ports? Mine were Very pitted!

Very dirty so far, gotta clean everything with a plastic blade and see the over all condition. Got some new Fel Pro gaskets and some BLACK RTV to seal everything nice and tight. I don’t know if this will fix my issue, but looking at the coolant ports, looks like they were gonna go soon anyway.

 

[east302]

Gasket remnants at 1 and 2 ports look pretty bad, did they break apart when you pulled the intake? It looks like the gasket has collapsed into the #2 port so the gasket job was probably overdue.

Those look like the old style gaskets without the metal reinforcing plate in the center.

That center tray in the lifter valley can be removed for cleaning underneath. Just don’t forget to put it back, lol. I did that once and had everything back together before I spotted it sitting there on the workbench.

 

[OilBurner2003]

Gasket remnants at 1 and 2 ports look pretty bad, did they break apart when you pulled the intake? It looks like the gasket has collapsed into the #2 port so the gasket job was probably overdue.

Those look like the old style gaskets without the metal reinforcing plate in the center.

That center tray in the lifter valley can be removed for cleaning underneath. Just don’t forget to put it back, lol. I did that once and had everything back together before I spotted it sitting there on I

I was honestly expecting worse condition, but, not sure if it’s gonna fix anything. I can pray it does when I get everything back together. At least it’s preventive maintenance! I snapped a vacuum line that goes to the PCV valve area, it’s the one that goes across the intake and into the firewall. I’ll need to try and find one somehow.

 

[east302]

GM part number below, likely discontinued since you’re looking for it.

Junkyard is probably the best bet. They weren’t supplied on pickups, just the SUVs. A vacuum hose kept off of any hot surfaces should be ok as well.

 

[OilBurner2003]

GM part number below, likely discontinued since you’re looking for it.

Junkyard is probably the best bet. They weren’t supplied on pickups, just the SUVs. A vacuum hose kept off of any hot surfaces should be ok as well.


View attachment 387638
View attachment 387639

Roger, I’ll probably go to the hardware store and pick some up as well!

 

[YukonGTmaster]

Roger, I’ll probably go to the hardware store and pick some up as well!

I would recommend using New Felpro intake bolts when re-assembling. They come with loctite Pre applied. Using a thread chaser and cleaning up internal threads is a good idea as well.

https://www.amazon.com/Fel-Pro-ES72224-Engine-Intake-Manifold/dp/B0039SOMUE/ref=mp_s_a_1_1?crid=IF24TTJVPWR0&keywords=felpro+72224&qid=1671328656&sprefix=felpro+72224%2Caps%2C147&sr=8-1