I'll go look and get back to you.

 

If it's the line running to the 4x4 actuator under the battery tray it shouldn't have vacuum unless the 4x4 is engaged. If it has a tiny bit of vacuum then likely the vacuum switch on top of the diff is bad and needs to be replaced or it will cause problems with the 4x4 not disengaging.

 

Could that be part of my rough idle problem?

 

If you look in this picture on the left middle side, there's a hose labeled #16 (parts list says 5/32" hose) with a #8 on the end that lolls like it doesn't connect to anything. Does that look like my hose?

 

Just looked, yes its hooked up, but badly dry rotted. Going to replace it. Mystery hose still unsolved.

 

Could it be one of the three that come off the 3 way switch for the 4wd?

**Edit**Traced it out to the 3 lines that come from the transfer case. It's the 7/32" vent hose. Look like it's been cut and left open for some reason. ugh.

Keep the ideas coming guys.

 

Did some troubleshooting. Took the hoses off the back if the intake and plugged it. it surged for a minute ten idled better, but still missed a little.

Also I plugged the mystery line that I think is the front diff 7/16" vent, didn't run any different, but when I took the plug out it sucked air pretty good. this don't sound right to me. do I have a bad three way switch?

Also unplugged the IAC and started it and the rpm started high and kept going up, so I killed the motor.

Any thoughts. I'm about to pull my hair out.

 

More troubleshooting. Made me a redneck smoke tester! Got a cigar an aquarium pump, some aquarium hose, and a rubber glove. Taped the glove over the throttle body butterfly hole, hooked the air pump (2 psi) up to the cruise control vacuum line with a three way so i could blow smoke in. Lit the cigar, blew smoke in plugged up the hole and turned the pump on. The glove expanded and heres what I found:

Vent tube off the xfer case was blowing air (the one that started this whole thread).
Plugged it, couldnt find anymore obvious leaks.
Turned the pump on again, blew a ton of smoke in and plugged the hole. Looked and looked for stray smoke around the intake, all the hose connections, the vac ball...nothing. Couldn't hear anything either. Even tried spraying a little soapy water everywhere, no bubbles.

Turned the pump off for a "bleed down test" it held pretty good. Pulled the vac hose off of the vac ball and smoke bellered out(good sign i guess?)

Conclusion? I think my xfer case three way switch is hosed and leaking vacuum, gonna replace it.

Any thoughts?

Doing a fuel pressure leakdown check tomorrow. Got a vacuum gauge coming in the mail just for a sanity check. Crossing my fingers.

 

Heres my quick smoke/pressure test rig. Works pretty good.

 

Did the leak down test today. Good news and bad news. The good news is, it shot up to 58-60 psig on the test gauge. Now the bad news:

8 mins later - 50 psig
15 mins later - 45 psig
35 mins later - 35 psig

It did something really weird the first time. It shot up to 60 psig, then bled all the way down to 10 psig in about 30 minutes. The numbers above were the second test.

Did a third test, pretty much same results as the second.

Ugh. Guess I need to re-open the plenum and take a look. Guess it could explain the rough idle. How the crap can a brand new AC Delco Spider assembly be bad?!?!?!?