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GLC250 4MATIC (X253.946) severe engine misfire / jerking when accelerating.

1189 Views 0 Replies 1 Participant Last post by  PeterM-GLC
Hello GLC forum.

My question relates to a 2018 (build July 2017), GLC250 4MATIC Australian delivered (steering drive shaft on the right).

I was wondering whether anyone has the Mercedes WIS procedure for replacing the crankshaft position sensor on this specific model ?


Purchased the car from the new car owner at 25,000 kms / 2+ years from new. The first issue noticed was the front wheel 'hopping/skipping' issue at high turn angles. Luckily I got the original Merc dealer to replace the front suspension 'knuckles' under warranty which cured this problem.

The next (and still current issue) relates to severe engine misfiring/drivetrain jerking when accelerating at medium to high throttle settings. Higher the throttle opening, higher the level of misfire/jerking and consequently, the reduction in power. Its a significant safety issue especially when attempting to overtake another vehicle, or even if moderate acceleration if required ie from the traffic lights. On one occasion, when using near full throttle to overtake, the engine started misfiring so badly, I needed to pull to the side of the road. I managed to limp home by manually selecting a low gear / high revs just to keep the engine running. No check engine light or logged ODBC codes after these misfiring events. Once cooled down overnight, the car returns to normal.

I've been living with the problem by driving at low levels of throttle but would like to fix the issue.

Possible fix.

After reviewing the forums, it appears the most probable cause is the Hall Effect crankshaft position sensor. When purchasing a replacement sensor, I noticed Mercedes have rolled the sensor part number possibly suggesting a product improvement or change of vendor, meaning the superseded part number might have a reliability issue - not sure ?

On the M274 engine, the crankshaft position sensor is apparently located near the engine/transmission flange on the RH lower side. Access (car on a hoist / underside panels removed) appears extremely difficult, especially as the 4MATIC drive shaft to the front wheels is very close to the engine. Visually, I can't see it or its wiring.

Before I attempt replacement, it would be great to understand the correct procedure, hence my request to forum members whether anyone has the appropriate Mercedes WIS procedure for replacing this crankshaft position sensor ?

Many thanks.
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