Quote:
Originally Posted by bradley
for a 1990. I want to keep the cruise control. Ihave read the threads but I guess I am old and get confused easily . could someone draw it out for me . for example do I keep the port throttle solenoid with the3 connector attached ???? do I have to run vacuum to the map sensor under the computer ?????? I just don't want to do the wrong thing .
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I am not a good drawer.....so I take photos.
You MIGHT want to also eliminate TB Coolant 
Starting at Item #2 (Eliminating Secondary Throttle Vacuum system) See LT5 Eliminated Systems
.
There are two vacuum sources (Electric Vacuum pump and Plenum).
Remove everything except the
diagnostic vacuum sensor that is located under the
ECM. The sensor is connected electrically and the hose nipple open to the atmosphere.
Remove all of the vacuum lines, the Secondary Vacuum Reservoir, the solenoid valve and the electric vacuum pump. Use
Marc Haibeck CHIP's
Marc Haibeck
Secondary Vacuum System
Diagnostic Vacuum Sensor
There are two
vacuum check valves under the plenum (one connected to
HVAC tank and one connected to
Secondary vacuum reservoir). The check valve connected to
HVAC tank (
via the "Y" cited below for
Eliminating Air Induction System) remains in position connected to passenger side source of plenum vacuum and connected to the
HVAC vacuum line in the harness to rear of plenum.
The check valve connected to the
Secondary Vacuum Reservoir and drivers side source of plenum vacuum can be capped off since the Secondary Vacuum Reservoir is eliminated. This is shown in the
Eliminating TB coolant system picture below.
3. Cruise Control/HVAC and EVAP Purge System.
The Cruize Control/HVAC Vacuum is taken from the passenger side of plenum. From there one vacuum line goes to the Cruize Control under ECM/Brake Cruize Vacuum Release (one line) and the second line goes to the HVAC System through the passenger side Fuel Injector Wire Harness (second line). The Vacuum line to the Cruize Control includes the
Cruize Control Vacuum Reservoir under Drivers side Headlight which is left in place. The other vacuum hose connected to the Cruize Control is for the brake pedal cruise cancel function.
The EVAP Purge system (1991 ZR1) draws vacuum from under front of Plenum and through the Solenoid valve. When the Solenoid valve is activated, vacuum is directed out the right side under Plenum back along the passenger side frame rail to the Charcoal Canister directly behind the Passenger Side rear wheel. The 1990 ZR1 Charcoal Canister is located under the Drivers Side Headlight. (Vacuum for the 1990 Charcoal Canister is taken from the drivers side front of Plenum as well as a vacuum line from beneath the front of the Plenum.
See Vacuum Systems 90' and 91' (Secondary and Cruize/HVAC)
Cruize Control and HVAC Vacuum System .....................EVAP Purge Vacuum System (1991) with Solenoid
Marc and Pete suggested to eliminate the EVAP Purge circuit completely and capping off that vacuum source under front of plenum. I just replaced my charcoal canister and Marc says he does not address that removal in the chip as it has no effect. I left that associated vacuum and electrical connection including the Evap Purge solenoid in place under the plenum.
This discussion and photo is for a 1991 which has the Charcoal Canister just to the rear of the passenger side rear wheel. The 1990 has the charcoal canister under the drivers side head light so the Vacuum Connections for Charcoal Canister are different as well as the vacuum lines which for the 1990 you will not find the large loop for charcoal canister under the Plenum. You will find the Plenum Nipple (Purge Vacuum Connection) on the 1990 is straight out of the plenum rather than angling back under the Plenum. On a 1990 you will also find a vacuum nipple angling back under the plenum from the Air Horn which provides vacuum depending on throttle position to the Purge Canister Control valve under the Drivers Side Head Light (1990 only).
