Trying to troubleshoot a hesitation issue when coming to a stop. My Blazer has had this weird issue where the RPMs drop way lower than they should when coming to a stop (almost stalling), or shifting into reverse and attempting to back-in to park.
I believe this is a sign of a vacuum leak, so I troubleshooted it as such.

It has a new fuel injection manifold and I rebuilt the whole intake manifold; new gaskets, o-rings, and vacuum hoses where applicable. For good measure I also did both the soapy water trick and the carburator cleaner trick around all suspected areas: plenum gasket, throttle body, air intake, MAF downstream, PVC, and purge solenoid (my Blazer doesn't have an EGR valve). Everything checks out; air tight seals.

I have a vacuum hand pump I used the test the accessory lines, and I found that the lines running after the first t-split from the vacuum solenoid don't hold vacuum. The vacuum line running under the fire wall (I assum to the transfer case) does hold vacuum, so no issue there. The line running to the HVAC controls does hold vacuum (well enough). But, the line running to the vacuum reservoir does not hold any vacuum. I have been unable to confirm if this device is suppose to be vacuumless or not. So, is this thing not pulling a vacuum when I go at it with a hand pump intentional design? If so, then I think my hesitation issue is not vacuum related.

 

Short answer, yes, the vacuum reservoir should be holding a vacuum.

There is also a one-way vavle in the Tee that should allow the vacuum system on the HVAC and vacuum reservoir to hold vacuum when the engine is under load such as when accelerating up a hill.

When I replaced my vacuum hoses I also used small zip-ties as mini hose clamps where the hoses attached to the nipples as a way to ensure no leaks.

 

@christine_208 In that case, it seems I found my vacuum leak. Now I just have to figure out how to access the inside of this fender. I imagine this device is a plastic box that has a crack in it.

 

It looks like I have to remove the whole ABS module to get to the vacuum reservoir to check it for damage (let alone replace it).
Does anyone have any reference material like a written procedure or video I can follow on how to remove such a deivce?
I'm having a difficult time finding anything on removing this device as well finding a replacement. Every part store I looked at online had nothing for a 2002 s10 vacuum reservoir.

 

The instructions from my 1999 GM Service Manual are attached.

I think the part you want is this: GM 15720833
https://www.gmpartsgiant.com/parts/g...tra2=&filter=()

Your only source for a vacuum tank is to find one in a wrecking yard or plumb in a universal substitute.
https://www.napaonline.com/en/p/NOE7301605

 

Quick check: It looks like you used the original hose that goes to the vacuum tank for your test. I had that hose in particular be the first to fail of the under-hood vacuum hoses in my Blazer. I'd suggest attaching a new hose directly to the vacuum tank to double check. It will be much easier than trying to pull everything apart to get at that vacuum tank!