Smart Fortwo Diesel: Rough Idle + Power Loss Fix Guide

Had similar symptoms on my Smart Forfour CDI from 2006. The rough running and jerking during acceleration pointed to a faulty fuel injector. The rich mixture was throwing off the air-fuel ratio, causing the check engine light and poor performance. The oxygen sensor readings confirmed the fuel mixture was way off. One injector was stuck partially open, leading to uneven fuel distribution in the intake manifold. This caused incomplete combustion and risked damage to the catalytic converter if left unfixed. Getting it sorted required removing and testing all injectors. One was indeed defective and needed replacement. The other injectors were cleaned and calibrated. The repair was essential since bad injectors can cause serious engine damage over time. These symptoms really match what you describe. Best get it checked soon, as running with a faulty injector can lead to cylinder damage and increased fuel consumption. The diagnostic process is straightforward for a qualified technician with proper testing equipment. The fix resolved all issues, no more stalling, smooth acceleration, and the engine light cleared. Would suggest having it looked at by a shop that specializes in diesel injection systems.

Thanks for sharing those details about the injector issue. That sounds exactly like what mine is doing. Did you remember roughly how much you paid for the full repair? Also curious if youve had any other fuel system problems since getting it fixed? The shop nearby quoted me 400€ just for diagnostics so trying to gauge if thats reasonable before booking it in. Been noticing the check engine light flickers sometimes before staying solid, not sure if that tells us anything extra about the throttle body or fuel injection system.

After having the repair done, I can confirm it cost 515€ total to fix the faulty injector. The mass airflow sensor readings are now perfect and the engine runs smoothly. The rich mixture problem was resolved completely after replacing the defective injection valve. The diagnostic fee you were quoted seems high compared to what I paid, especially since my total repair including parts and labor was just slightly more. A proper fuel injection system check including testing the intake manifold and injectors should cost less. Since the repair 8 months ago, I have not experienced any fuel system issues. The check engine light has stayed off and the engine maintains steady power. The flickering light you mentioned could indicate an intermittent fuel delivery problem, but the mechanic will need to run proper diagnostics to confirm. I would suggest getting a second quote from another shop that specializes in fuel injection systems. The symptoms match exactly what I experienced, and proper repair resolved all the issues completely.

I finally took my Smart to get checked out. Found a diesel specialist who only charged 180€ for diagnostics. Turns out you were spot on, it was a faulty injector causing the rich mixture problems. The mass airflow sensor readings were all over the place because of it. The mechanic showed me how one injector was stuck partially open, messing up the fuel flow through the intake manifold. Total repair came to 650€ including parts and labor. They replaced the bad injector and cleaned the others while they were at it. Been driving it for a week now and what a difference. No more check engine light, engine runs smooth as new, and no more stalling. Even my fuel economy has improved. Glad I got it sorted before it could damage the catalytic converter or cause bigger issues. Thanks again for helping me diagnose this. Could have spent way more if I had gone in blind without knowing what to expect.