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6-1 2
1977 PONTIAC SERVICE MANUAL
I. Poor Gasoline Mileage
1. Wih engine running, remove air cleaner
cover and filter. Check filter for dirt or
being plugged. Replace as necessary.
Damper door in air cleaner snorkel should
be closed when engine is cold. It may be
necessary to place cold wet rag over sensor to
close it if engine is too warm.
If damper door does not close, apply vacuum
directly to vacuum motor.
If door closes, replace sensor. If door
stays open, replace vacuum motor.
2. Visually check the following:
a. Vacuum hoses for splits, kinks and proper
connections. See hose routing charts,
Section 6E.
b. Air leaks at carburetor mounting and intake
manifold.
c. Ignition wires for cracking, hardness and
proper connections. Repair or replace as
necessary.
3. Check ignition timing per emission control
information label. Disconnect and plug vacuum
advance hose.
NOTE: To check mechanical advance, observe
timing mark. It should advance as throttle
is opened and return to mark as throttle is
closed.
4. Check carburetor choke linkage and settings.
Clean and repair as necessary. See carubretor
choke adjustments, cleaning and inspection,
Section 6C.
5. With engine off, remove vacuum hose from
distributor vacuum advance. Connect vacuum
pump and apply 15" vacuum. Vacuum should
hold steady for 15 seconds. If vacuum drops,
replace vacuum advance unit.
6. Remove spark plugs, check for cracks,
wear, improper gap, burned electrodes, heavy
deposits.
Repair or replace as necessary.
7. If in previous checks, adjustments have
not been made that could improve mileage,
remove carburetor air horn and check the
following:
a. Power piston for freeness
b. Din in jets and metering passages
c. Metering rods
d. Power valve(s)
e. Float adjustment
See carburetor cleaning, inspection, and
adjustments, Section 6C.
8. Suggest owner fill tank and recheck mileage.
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