Navistar N9 Diagnostic Manual page 39

1 DIAGNOSTIC TROUBLESHOOTING PROCEDURES
Step 3 Record snapshot of engine running data and determine if engine idles properly.
Perform Record Snapshot of Engine Running Data (page 2113) while symptom is occurring.
A. Run engine at idle.
B. Full throttle for 15 seconds.
C. Idle for 30 seconds.
D. Full throttle for 15 seconds.
E. Idle for 30 seconds.
F. Stop recording.
Does engine idle rough or surge at idle?
Step 4 Determine if engine is able to reach rated speed.
A. Start engine.
B. Increase engine rpm to rated speed, and return to idle.
Is engine able to reach rated speed?
Step 5 Determine if a popping noise is coming from engine air intake.
A. Start engine.
B. Listen for popping noise from engine air intake.
C. Increase engine rpm to rated speed and return to idle.
Is popping noise heard from engine air intake?
35
Decision
Yes: Go to 4.1 Rough Idle
(page 66).
No: Go to Step 4.
Decision
Yes: Go to Step 5.
No: Go to 4.2 Engine
Unable to Reach Rated
Speed (No Load) (page
70).
Decision
Yes: Go to 4.3 Popping
Noise from Intake (page
72).
No: Review operator
complaint.