🚗 Classic Fault — Mercedes-Benz W124 (1984–1997)
W124 M103 rough idle and stalling — idle control valve
💰 Estimated Repair Cost
$30 – $100 GBP
Parts and labour estimate
🔧 Tools Required
Carb cleaner, multimeter
📋 Overview
The auxiliary air valve and idle control valve on the M103 six-cylinder fail with age, causing rough or hunting idle.
🩺 Symptoms
- Rough idle
- engine stalls at junctions when warm
- idle surges between 500-1500rpm
- improves when valve unplugged
🔍 Possible Causes
- Failed idle control valve
- dirty throttle body
- air leak at inlet boot
🛠️ Diagnosis Steps
Unplug idle control valve — if idle stabilises valve is suspect. Clean throttle body bypass port.
✅ Most Confirmed Fix
Idle control valve replacement
86% of users confirm this fix worked (34 reports)
🔗 Other Mercedes-Benz W124 Faults
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