Black smoke, rough idle and limp mode in town traffic
- Make and model
- Fiat Punto Evo
- Year
- 2010
- Engine
- 1.3 Multijet 75
- Fuel
- Diesel
- Mileage
- 150,000 km
Customer complaint
Black smoke when pulling away, a rough idle, and the car goes into limp mode after a few minutes in town traffic. Better on the open road.
IdleShort trips
Fault codes
| Code | Description | Status |
|---|---|---|
| P0404 | Exhaust Gas Recirculation "A" Control Circuit Range/Performance | Confirmed |
Measurements and live data
| Parameter / measurement | Measured | Expected |
|---|---|---|
| EGR position, specified / actual, idle | 0 % / 35 % | actual follows specified |
| Measured air mass, idle, as % of specified | 62 % | close to 100 % |
Tests performed
- EGR actuator test with a scan toolValve slow to close and stops at about 30 % open
- EGR valve removedThick carbon on the seat and stem
Solution
Root cause
EGR valve sticking partly open with carbon from short trips.
Repair
Cleaned the intake, fitted a new EGR valve and ran the EGR self-learn with the scan tool, then cleared the code. Smooth idle, no smoke, measured air mass back to specified.
Parts
EGR valve and gasket
Labour time
1.5 h
Lesson learned
An EGR valve stuck open shows up as low measured air mass at idle: compare specified and actual before blaming the MAF.
Training case: the usual fix for this fault, not a confirmed repair on a specific car.
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