Piper Navajo PA-31 Service Manual page 515

Incorrect idle adjustment.
Uneven cylinder compression.
Faulty ignition system.
Insufficient fuel pressure.
Internal injector leak (usually
unable to adjust injector at idle).
Fuel vaporizing in lines and
distributor (encountered only
at high ambient temperatures
and prolonged operation at
low or idle RPM).
Nozzle screen and shroud
deformed so that it blocks air
bleed hole.
Sticking valve in fuel flow
divider.
Primer leaking or not locked.
PIPER NAVAJO SERVICE MANUAL
TABLE VIII-II. TROUBLESHOOTING CHART (ENGINE) (cont.)
Trouble
Cause
Remedy
Failure of engine to idle
properly.
Incorrect idle mixture.
Leak in the induction system.
Adjust mixture.
Tighten all connections in the
induction system. Replace any
parts that are defective.
Adjust throttle stop to obtain
correct idle.
Check condition of piston rings
and valve seats.
Check entire ignition system.
Adjust fuel pressure.
Replace injector.
Keep ground operation to
minimum and operate with
cowl flaps fully open.
Replace nozzle.
Disassemble and clean.
Replace primer if leaking or
lock securely if loose.
ALSO SEE CAUSE AND REMEMDY AT "ROUGH ENGINE".
Low power and uneven
running.
Mixture too rich as indicated
by sluggish engine operation,
red exhaust flame at night.
Extreme cases indicated by
black smoke from exhaust.
Readjustment of fuel injector
by authorized personnel is
indicated.
Mixture too lean; indicated
by overheating or
backfiring.
Check fuel lines for dirt or other
restrictions. Check fuel injec-
tion nozzles.
POWER PLANT
Revised: 9/24/81
2J17