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