Mercedes A Klasse rough idle on cold start

My 2008 Mercedes A Klasse with a gasoline engine is giving me headaches. 165290 km on the clock. Starts rough when cold, idles like it's about to stall, but smooths out after a few minutes. I suspect a faulty cold start injector. I did some digging and it seems like a possible injector issue affecting fuel delivery during the cold start phase. Any thoughts on how to confirm this? I'm thinking injector test, checking the fuel rail, maybe even looking at the entire fuel system? Could this be just a defective injection valve?

4 comment(s)

Sounds familiar. I had similar rough idle on my A Klasse. Is it like a sputtering, almost like the engine's missing a beat? If so, it could be the injector. Have you considered the fuel filter?

Yeah, sputtering is a good way to describe it. The engine definitely feels like it's missing. The fuel filter is relatively new, but I guess it wouldn't hurt to double check. When you had this, was it affecting all injectors or just one? How did you pinpoint the culprit? Did you do an injector test or something else?

Just one injector was causing the grief. I didn't mess with it myself - I took it to a shop. They ran some tests, confirmed the bad injector, and replaced it. Problem solved. Honestly, messing with the fuel system can be tricky, like playing operation. One wrong move and you're in trouble, and the engine is the patient. If you have any doubts, take it to the shop, could save you a headache.

I appreciate the advice. I was hoping to avoid the shop, but you're probably right. Fuel system stuff can get complicated fast. I ended up taking it in. Turns out it was indeed a faulty injector. It cost me 515€ to get it sorted, including the injector test and replacement. Runs smooth as butter now, even on cold starts. Thanks!

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