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I am reassembling the intake system after a fuel injector swap. The issue I ran into is my son disassembled the intake and did not label the vacuum lines. Which typically would not be a big deal expect a previous owner did a intake swap from a C4 and the lines are not quite standard. I have figure out most of it but I seem to have an "extra" port on the intake plenum as shown below. What is this use for normally on a 91 z28 5.7? Also attached is the lines available and were I think they go. It just seems like either the 2nd port on the Plenum was open or something is missing.
I don't understand how this stuff gets mixed up like this... The tube on the MAP sensor is formed, it can only reach one port, and one of the two toward the rear. The FPR goes to the other. They should pretty much just fall into place. From the EGR solenoid you have two hoses, the long one goes to the bottom of the throttlebody, the short one goes to the EGR valve. The bigger hose barb is the vacuum source for the HVAC and Cruise Control. They're almost hard to hook up wrong, because the formed lines naturally fall into place, and the larger Hvac/cruise vacuum hose is the only one that should fit on the larger barb.
Drew, I think a previous owner changed it up as my Havc is actually t-d into the line labeled map
It's sure possible. Looks like someone bolted the fuel rail down with runner bolts, and obviously the Corvette style EGR tube...
Find the vacuum line from the driver's side of the engine bay, up in front of the inner fender you should see a rubber line from under the car coming from the vacuum reservoir ball, and there should be a Tee where it joins in with the vacuum line from the cruise control servo. It'll snake back to the firewall, and over to the intake with the rats nest of harnesses and whatnot at the back of the engine. Just before it ends, that tube should meet up with the shorter of the two hard tubes coming out of the firewall behind the passenger's side head. The HVAC hose, and the Vacuum line to the reservoir/cruise control should connect to two of the connections on this fitting - see image -
The third line from that fitting goes to the big barb on the plenum. The MAP and FPR each have their own barbs.
Here's another pic showing how the three way tee/check valve is oriented, admittedly it's not the best, but try to bear with me...
Keep in mind that in this pic, I was in the process of stripping the car and pulling the engine, so the HVAC harness and lines were pulled out of the firewall. Note the short hard line with the 90* rubber fitting, just above the strut tower. The Tee/Check valve is a couple inches below the 90* rubber fitting. The stubby hose coming off the side pointed towards the engine goes to the vacuum reservoir and cruise control servo. The larger tube disappearing behind the strut tower would connect to the plenum normally. Even on the V6 pictured, the MAP has it's own barbed fitting on the plenum.
04-06-2019, 01:30 PM
