Mercedes A Klasse Diesel Engine Issue Resolved

It certainly sounds like a glow control unit issue could be the culprit, particularly with those symptoms. Think of the glow plugs like a small pre-heater for each cylinder, helping with a smooth cold start. If the control unit isn't working correctly, or if there's a faulty connection, the engine might struggle, causing the smoke and engine misfire. Have you had a diagnostic test done to confirm the fault code? It's important to rule out other potential issues before replacing the control unit.

A diagnostic test? Where do I get one of those done? And if it is the control unit, is it something easily fixed? Like, could it just be a loose wire or is it definitely the whole control unit needs replacing?

A diagnostic test can be performed at most workshops. They'll plug in a device that reads the car's computer and tells you what's wrong. Regarding the control unit, a defective cable or plug connection is indeed a possible cause. It's like a lamp that doesn't light up because the plug is loose. However, the control unit itself could also be faulty. It's best to have it properly inspected. If you aren't comfortable doing it yourself, I'd recommend taking it to a workshop. They can confirm whether it's the wiring or the control unit that's defective.

Thanks for the advice! I took it to a mechanic. The diagnostic test pointed to the glow control unit. Turns out it was a corroded connector. They cleaned it up and all is working again. Cost me 95€, so not too bad!