P0506moderate severityPowertrain
Idle Air Control System RPM Lower Than Expected
on 1998 Audi A8 4.2L V8 · AWD
What this code means
The idle speed is consistently below the target RPM.
Symptoms
- Low idle speed
- Stalling
- Rough idle
Common causes
- Carbon buildup in throttle body
- Vacuum leak
- Faulty IAC valve
- Low fuel pressure
- EGR valve stuck open
Diagnostic steps
- Clean throttle body
- Check for vacuum leaks
- Test IAC valve
- Test fuel pressure
- Check EGR valve
Repair notes
Clean throttle body and IAC. Check for vacuum leaks.
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