Case Type: Technical Diagnostic Case Analysis
Application: EGR-Equipped Diesel Engine
Diagnostic Focus: Air-Path vs Fuel-Delivery Diagnosis
Rough idle combined with cylinder correction values can quickly lead to injector replacement.
But abnormal intake dilution can also change cylinder combustion.
Combustion quality depends on both:
fuel delivery
and
available air / oxygen condition.
A disturbance in either side can create similar driver complaints.
Relevant data may include:
Correction values show ECU compensation.
They do not independently prove the injector created the original combustion imbalance.
For a broader diagnostic framework, see Technical Insight: Why EGR Flow Problems Can Mimic Diesel Injector Combustion Faults.
Rough idle diagnosis should compare fuel-delivery evidence with air-path control before an injector is condemned.
