Good morning all! I am having an issue with my 1995 G20, 350 TBI, Van. It's name is Stubby. Here's what stubby is doing:

When I reach ~ 60 mph, I start losing the air from my vents and it begins going to my feet and windshield. At 65+ I have no air to vents and it's 98% to the floor and windshield. I also feel like the van has lost a little power when it's doing this as well.

I've read that this is most likely a vacuum leak somehwere, so I've been mainly troubleshooting that.

Here's what I've done. I have replaced a small check valve in one of the vacuum lines that goes from the intake manifold to the Vacuum Ball and the AC head unit. (see my first pic, it's the white valve) (The second pic is where that hose goes - it illustrates it coming from back of engine to ball / AC)

Replacing that valve did not fix. Next, I used the carb cleaner spray method around all hoses and manifold and did not get any results (going to try this again). I also attempted the smoke method with a cigar to blow smoke into the same hose at the valve in my first pic. The smoke just exited the intake right where the injectors are from a hole that is supposed to be there.

I'm about out of options that I know what to test for and where to look, so I'm open to any and all ideas on what and where this problem could be. Thanks!!

 

The material is so cheap, that instead of spending hours troubleshooting, I would just replace all the vacuum components, especially the thin hard plastic lines. They get brittle from the heat and form invisible cracks. The reservoir too.

If that doesn't help then the problem lies either in the control head or actuators.

 

That's not a bad idea. I already snapped a very brittle hose on the manifold (EGR hose I think) and had to replace it.

 

UPDATE: I cut off the exhaust from the headers back (removing the cat) and ran straight 3" pipe from the Y-Pipe to the rear axle (this is temporary btw). This seems to have solved the issue almost completely. I drove about 50 miles, mostly highway. Air blows hard from vents no matter what speed or how hard I accelerate. Some power came back at higher speeds. No need to drop gears just to increase speed from 55mph+ up to whatever. I still feel like there should be more power from this old 350, but that might be a different issue.

The main point is, after removing the cat this solved the original issue I posted here. File this as solved for now. If I chase down the power loss I'll make a different thread with more details if necessary. Hope this helps others!

 

The EGR valve was probably stuck open

 

Seems like there is a way to test the EGR, make it fully open and close.

Or just replace it, if you can find one reasonable.