IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
12-30
March 2020
Page 85
IO-390-D Series Engine Maintenance Manual
Table 1 (Cont.)
Fault Isolation Guide
Problem
Cause
Corrective Action
Ref.
Rough Idle (Cont.)
Lycoming Electronic
Ignition System (EIS)
Refer to the “EIS Troubleshooting
Guide” in this chapter.
Low cylinder
compression
1.
Complete the “Cylinder Compression
Check Procedure.”
2.
Complete a “Borescope Inspection
Procedure” on low-pressure
cylinder(s).
72-30
Blocked injection
nozzles
1.
Identify whether the cylinder with
the suspected blocked injection
nozzle is cold or hot. (The cylinder
will be cold after 2 minutes of engine
operation.)
2.
Complete the “Injection Nozzle Fuel
Flow Check.”
3.
Complete the “Injection Nozzle
Removal” procedure.
4.
Complete the “Injection Nozzle
Cleaning” procedure.
5.
Complete the “Injection Nozzle
Installation” procedure.
73-10
05-30
73-10
Leak in induction system Complete the “Induction System
Inspection” procedure.
72-80
Internal fuel injector leak Complete the “Fuel Injector Leak
Check” procedure.
73-10
Cracked engine mounts
or defective mount
bushings
Replace engine mounts or bushings.
AMM
Engine mount bushing
incorrectly installed
Install the engine mount bushing
correctly.
AMM
Loose ignition lead(s)
Make sure all ignition leads are secure.
Lean idle mixture
1.
Adjust the idle mixture the "Idle
Speed and Mixture Adjustment”
procedure.
2.
Readjust the idle speed.
72-00