S10/T10 Blazer 4WD V6-173 2.8L VIN B 2-bbl (1983)
6. Reinstall carburetor on engine:
a. Do not install air cleaner and gasket.
b. Disconnect the bowl vent line at carburetor.
c. Disconnect the EGR valve hose and canister purge hose at the carburetor and cap the carburetor ports.
d. Refer to Vehicle Emission Control Information label to disconnect temperature sensor on air cleaner and secondary vacuum break TVS switch,
plug open hoses
e. Connect a dwell meter positive lead to the mixture control solenoid dwell test lead (green connector). Connect other lead on meter to ground.
Set dwell meter to 6-cylinder position. Connect a tachometer to distributor lead (brown connector). (Tachometer should be connected to the
distributor side of the tach filter if vehicle is equipped with a tachometer).
f.
BLOCK DRIVE WHEELS.
g. Place transmission PARK (automatic transmission) or NEUTRAL (manual transmission) and set the parking brake.
7. Proceed to Mixture Adjustment Procedure.
Lean Mixture And Idle Mixture Adjustments
MIXTURE ADJUSTMENT PROCEDURE:
1. Pre-set carburetor following procedure above.
2. Run engine on high step of fast idle cam until engine cooling fan starts to cycle. (At least three minutes and until in closed loop).
3. Run engine at 3,000 RPM and adjust the lean mixture screw slowly in small increments--allowing time for dwell to stabilize after turning the
screw--to obtain an average dwell of 35 degrees.
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If dwell is too low, back screw out; if too high, screw it in.
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If unable to adjust to specifications, inspect main metering circuit for leaks, restrictions, etc.
NOTE: The dwell reading of the M/C solenoid is used to determine calibration and is sensitive to changes in fuel mixture caused by heat, air
leaks, etc. While idling, it is normal for the dwell to increase and decrease fairly constantly over a relatively narrow range, such as 5 degrees.
However, it may occasionally vary by as much as 10-15 degrees momentarily due to temporary mixture changes. The dwell reading specified is the
average of the most consistent variation. The engine must be allowed a few moments to stabilize at idle or 3,000 RPM as applicable before taking
a dwell reading.
4. Return to idle.
5. Adjust idle mixture screw to obtain an average dwell of 25 degrees with cooling fan in off cycle. If reading is too low, back screw out. If too high,
turn it in. Allow time for reading to stabilize after each adjustment. Adjustment is very sensitive. Make final check with adjusting tool removed. If
unable to adjust to specifications, inspect idle system for leaks, restrictions, etc.
