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PART
8-1-
GENERAL ENGINE SERVICE
8-5
DIAGNOSIS GUIDE (Continued)
ENGINE RUNS, BUT
MISSES (Continued)
ROUGH ENGINE IDLE
POOR ACCELERATION
ENGINE DOES NOT
DEVELOP FULL POWER,
OR HAS POOR HIGH
SPEED PERFORMANCE
Restricted fuel filter.
Restricted main fuel system.
Positive
crankcase
ventilation
system restricted or not operating
properly.
IGNITION SYSTEM
Defective spark plugs.
FUEL SYSTEM
Engine idle speed set too low.
Idle fuel mixture needle(s) not
properly adjusted.
Float setting
incorrect.
Air leaks between the carburet-
tor, spacer and the manifold and/or
fittings.
Intake
manifold
gasket
leak
(V-8).
Fuel leakage at the carburettor
fuel bowl.
Power valve leaking fuel (V-8).
Idle fuel system air bleeds or
fuel passages
restricted.
Fuel bleeding from the accelera-
ting pump discharge nozzles.
Leaking fuel pump, lines or fit-
tings.
IGNITION SYSTEM
Incorrect ignition timing.
Fouled or
improperly
adjusted
spark plugs.
Improperly adjusted or defective
breaker points.
Distributor not advancing prop-
erly.
FUEL SYSTEM
Accelerating pump
malfunction.
Jo'loat setting incorre.:t.
Throttle linkage not properly ad-
justed.
Accelerating
pump
stroke
not
properly
adjusted.
Leaky power valve, gaskets or
accelerating pump diaphragm.
Power valve piston stuck in the
up position (6-cylinder and 302 V8).
FUEL SYSTEM
Restricted air cleaner.
Restricted fuel filter.
Clogg·ed or undersize main or sec-
ondary jets or low float sett'ing.
Power valve or passages clogged
or damaged.
Fvel pump pressure
incorrect.
Power valve piston stuck In the
up position (6-cylinder and 302 V8).
Automatic.' choke malfunctioning
or improperly adjusted.
COOLING SYSTEM
Engine
overheating.
ENGINE
Perfol'm a man ifold vacuum or
compression
test
to
determine
which mechanical component of the
engine is at fault.
IGNITION SYSTEM
Improperly adjusted or defective
breaker points.
Fouled or improperly adjusted
spark plugs.
Incorrect ignition timing.
Spark plug
misfiring.
ENGINE
Loose engine mounting bolts or
worn engine support insulator.
Cylinder head bolts not properly
torqued.
Valve clearance set too tight.
Crankcase
ventilation
regulator
valve defective or a restricted vent
tube.
Worn camshaft lobes.
Perform a manifold vacuum or
compression
test
to
determine
which mechanical component is at
fault.
Dirt or corrosion in accelerating
system.
Restricted fuel
filter.
Defective fuel
pump.
BRAKES
Improper adjustment-too tight.
TRANSMISSIONS
Clutch
slippage
(manual
shift
transmissions.
Improper band adjustment (auto-
matic transmissions)
.
Converter One-Way Clutch (auto-
matic transmissions).
ENGINE
Perform a manifold vacuum or
compression
test
to
determine
which mechanical component of the
engine is at
fault.
IGNITION SYSTEM
Ignition timing not properly ad-
justed.
Defective coil, condenser or
rotor.
Distributor not advancing prop-
erly.
Excessive play in the distributor
shaft.
Distributor cam worn.
Foule.
d
or improperly adjusted
spark plugs, or spark plugs of in-
correct heat
range.
Impl'operly
adjust
ed or defective
breaker points.
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