Bonneville V6-231 3.8L VIN 3 SFI (1988)
Idle Speed: Adjustments
Idle Speed
Midpoint of range given is the preferred setting speed.
If no specifications are listed under "Minimum Speed", the idle is not adjustable.
1982-86 All W/single TBI: Gain access to throttle stop screw. With engine at operating temperature, disconnect idle air controller and install special
tool to seal idle air passage of throttle body. Turn throttle stop screw to specified minimum speed value.
All W/dual TBI: Disconnect IAC electrical lead. Start engine and let idle speed stabilize. Remove cap on rear TBI unit and connect a water manometer.
Adjust minimum speed to achieve 6" of water on scale in drive. Reinstall cap on rear unit and remove cap on front TBI unit. If reading is not 6" of water,
adjust balance screw on linkage. Disconnect manometer and set minimum speed on rear TBI unit to specified value.
1982-86 All W/Fuel Injected except TBI; 1987-90 All W/Fuel Injected & TBI and when specifications are listed in Minimum Speed column:
1.8L (112) Turbo, disconnect PCV valve hose and allow engine to draw air for two minutes. Disconnect IAC electrical lead and set minimum speed to
specifications. All others, ground diagnostic lead and turn ignition on for 30 seconds. Remove IAC lead and remove ground from diagnostic connector.
Start engine and set minimum speed to specified value.
All carburetted W/ISC: With engine at operating temperature, turn ignition off and disconnect harness from ISC. Apply 12 volts (+) to third terminal
from top of ISC (C), and ground the fourth terminal from top (D) only long enough to retract ISC plunger. With engine running, set minimum idle to
specifications by adjusting carb base screw. Apply 12 volts(+) to fourth terminal from top of ISC (D) and ground the third terminal from the top (C) only
long enough to fully extend the ISC plunger. Set maximum speed to specifications by turning ISC plunger head.
NOTE: Never apply voltage to first two upper terminals (A & B) or damage to the unit will result.
All carburetted W/ILC: Disconnect and plug vacuum hoses at EGR and canister purge valves. With engine at operating temperature, remove vacuum
hose from ILC and plug. Set maximum speed to specifications by holding hex nut and turning plunger shaft. Reconnect ILC vacuum hose and check
that minimum speed is correct. To adjust, remove rubber and metal plugs from rear center outlet tube, insert a 3/32" Allen wrench. Remove ILC hose
and plug. Connect a remote vacuum source and apply vacuum to the unit. Adjust carb base screw to obtain minimum speed.
