18
Drivability
Condition
Warm Engine
Drivability
Condition
(Cont.)
4) Ignition timing retarded.
4) Set to factory specs. Make sure advancing correctly.
5) Idle speed set too fast &
mixture is too lean (common)
5) Richen up the idle mixture, reset the idle speed to factory
specs, then reset the mixture using the lean drop method.
6) EGR valve stuck on or coming
on too early (hose on wrong?)
6) Inspect hose routing to EGR valve & inspect valve. Replace
as necessary.
Doggy, runs rough,
lots of black smoke
at idle.
1) Choke staying closed or partly
closed.
1) Fix choke or heat source.
2) Slow flooding.
2) Fix cause of flooding.
3) Step-Up Piston up in bore
3) Remove step-up piston and fix sticking issue or use a lighter
step-up spring
4) No power to choke.
4) Repair as necessary.
5) Secondary Air Door or Goggle
Valve stuck or partially open
5) Find cause and repair
Hesitation under
heavy throttle:
Dead spot &
stumble. May
backfire or spit
back.
1) Defective accelerator pump.
1) Look for dirt in pump nozzles, swollen cup from bad gas, or
check ball missing or stuck.
2) Metering rods sticking/binding.
2) Repair as necessary.
3) Vacuum leak.
3) Locate leak and repair.
4) Float level setting very low.
4) Reset to factory specs. Factory setting, with air horn upside
down, is 1.01”+/- .015” from the cast surface to bottom of float.
5) Plugged up fuel filter, defective
fuel pump, or swollen or kinked
lines.
5) Inspect and repair as necessary.
6) Secondary air valve set wrong.
6) Check & adjust the secondary air valve spring.
7) Ignition timing retarded.
7) Set to factory specs. Make sure advancing correctly.
Poor
Performance
or Gas
Mileage
No power or bad
gas mileage.
1) Plugged exhaust.
1) Check exhaust. Look for plugged catalytic converter, bad
muffler baffle, kinked or crimped pipe, dirt or other foreign
matter in pipe.
2) Clogged gas tank vent, or fuel
venting system.
2) Remove gas cap & see if performance improves. If so clean
or replace the gas cap. Check the charcoal canister, hoses to it
& any check valves. Check the electric vent valve on the carb if
there is one, & make sure it is getting power at the right time.
3) Ignition timing retarded
3) Check timing at idle and also for full advance when revved
up. Look for bad or loose hose, hose hooked up to wrong pipe
on distributor, bad thermal switch, leaking vacuum advance can
on the distributor, a worn breaker plate, worn distributor shaft,
sticky weights, point gap closed up, etc.
4) Clogged air filter
4) Replace air filter.
5) Choke not opening
5) Fix choke or power source problem.
6) Secondary not opening.
6) Check for sticky or bent shaft or linkage. Check secondary air
door, check the spring tension & metering rods for dragging or
sticking.
7) Wrong main jets or rods.
7) Check and replace, as necessary.
8) Dragging brakes.
8) Fix brake problem.
9) Low tire pressure.
9) Increase tire pressure to factory specs.
10) Automatic Transmission
malfunction.
10) Diagnose & fix automatic transmission.
11) Wrong or malfunctioning
thermostat in cooling system.
11) Replace thermostat.
12) Blocked or leaking exhaust
heat passage in intake manifold.
12) Remove manifold & fix it.
13) Defective accessory (power
steering pump, air conditioning
compressor, etc.) causing drag
on engine.
13) Diagnose & repair or replace the accessory unit.
14) Wheels out of alignment.
14) Have wheels professionally aligned.
