majablaze8
Mercedes ML rough cold start issue
Summary of the thread
A 2015 Mercedes ML was experiencing rough running during cold starts, potentially due to a faulty cold start injector causing engine misfire and poor fuel delivery. The check engine light was on, but diagnostic trouble codes had not been checked. It was suggested to use an OBD II scanner to retrieve codes and listen to the injectors with a mechanic's stethoscope to confirm electrical operation. Ultimately, a shop confirmed a faulty injector, replaced it, and resolved the cold start issue.
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4 comment(s)
majablaze8 (community.author)
The check engine light is on. I haven't checked the codes yet, and I haven't touched the fuel filter. What kind of injector test are we talking about? Can I do it myself?
julian_lehmann1
Get the diagnostic trouble codes (DTCs) with an OBD II scanner. Many auto parts stores will do this for free. For the injector test, you can listen to each injector with a mechanic's stethoscope while the engine is running to see if they are clicking. This confirms electrical operation, not fuel delivery. A more comprehensive test needs equipment to measure fuel injector flow rates and spray patterns. I advise taking your vehicle to a qualified workshop for diagnosis and repair. A defective injection valve/injector is a likely cause.
majablaze8 (community.author)
I took it to a shop, and they confirmed it was a faulty injector. They replaced it, and the cold start issue is gone. Cost me about 515€.
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MERCEDES
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ML
julian_lehmann1
Poor engine running during cold starts in your Mercedes ML could be caused by a defective cold start injector. This provides extra fuel during start-up. If it's not working right, it can cause a lean fuel mixture.