🚗 Classic Fault — Toyota (1984–1989)
MR2 Mk1 3A-U carburetor diaphragm failure
💰 Estimated Repair Cost
$15 – $60 GBP
Parts and labour estimate
🔧 Tools Required
Carb rebuild kit, screwdrivers
📋 Overview
The accelerator pump diaphragm in the 3A-U carburettor tears and causes a flat spot on acceleration.
🩺 Symptoms
- Hesitation and stumble on quick acceleration from idle
- fine under steady throttle
- black smoke on acceleration
🔍 Possible Causes
- Torn accelerator pump diaphragm
- blocked main jet
- stuck float
🛠️ Diagnosis Steps
Remove carb top and inspect accelerator pump — pump manually with screwdriver while watching for fuel squirt into bore
✅ Most Confirmed Fix
Carb accelerator pump diaphragm replacement
86% of users confirm this fix worked (25 reports)
🩺 Related Symptoms
🔗 Other Toyota Faults
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