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romylion2

GLC Hybrid Engine Misfiring Issue

Has anyone else experienced engine misfires on a 2017 GLC Hybrid

Summary of the thread

A 2017 GLC Hybrid experienced engine misfiring, indicated by rough idle, a flashing check engine light, and jerking during acceleration. The issue was initially suspected to be related to ignition coils or the fuel pump, but both were found to be functioning correctly. The diagnostic code P0300 suggested a random multiple cylinder misfire, leading to the identification of a defective fuel injector as the root cause. Replacing the faulty injector resolved the misfiring issue, restoring smooth engine operation.

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4 comment(s)

lauraheld48

I have a GLC too and had a similar experience: rough idle, check engine light flashing, occasional jerking when accelerating. Engine misfiring can come from a few things. Have you checked the ignition coils? A bad coil can cause incomplete combustion, leading to misfires. Also, think about the fuel pump. Not enough fuel can also cause misfires, especially at higher RPMs. What diagnostic codes are you getting from the check engine light?

romylion2 (community.author)

I appreciate the insight. Ignition coils seem fine, resistance is within spec. Fuel pump seems okay, but I haven't done a proper pressure test. The code I'm getting is P0300 Random Multiple Cylinder Misfire. Any thoughts?

lauraheld48

P0300 is a vague code. Since the ignition coils seem okay, and you suspect the fuel pump, the next most likely thing, in my experience, is a bad fuel injector. Fuel injectors spray a precise amount of fuel into the cylinders. If one is clogged or not working right, it can cause a lean condition, leading to misfires. A lean condition means there isn't enough fuel in the air-fuel mix for proper combustion. Given your symptoms, I'd suggest having the injectors looked at. I'd advise you to visit a trusted workshop.

romylion2 (community.author)

Thanks for the suggestion! It was a defective fuel injector. I replaced it, and the engine runs smoothly again. Total cost was 515€ for the injector and labor.

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