🚗 Classic Fault — Mercedes-Benz (1976–1985)
W123 K-Jetronic warm-up regulator failure
💰 Estimated Repair Cost
$40 – $150 GBP
Parts and labour estimate
🔧 Tools Required
CIS pressure gauge set
📋 Overview
The warm-up regulator on 230E models controls fuel enrichment when cold. When it fails, mixture is wrong at all temperatures.
🩺 Symptoms
- Rich running when warm
- poor economy
- black plugs
- hunting idle
- engine runs better when cold
🔍 Possible Causes
- Failed warm-up regulator bimetal
- incorrect control pressure
- blocked regulator
🛠️ Diagnosis Steps
Test control pressure with CIS gauge set — warm control pressure should be 3.4-3.8 bar. Cold should be lower
✅ Most Confirmed Fix
Warm-up regulator replacement
80% of users confirm this fix worked (18 reports)
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