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RPMs start to fluctuate (more like large drop and back to 700 RPM and again drop and back to 700 and so on, but overshoot is not so evident) when coming to a stop only in window between 35-50 km/h and in neutral, meaning clutch not pressed in.

Observations:

  • If the clutch pedal is pressed in the RPMs stop fluctuating immediately.
  • RPMs won't even start to fluctuate if I come to a stop with clutch pressed in all the time.
  • RPMs fluctuate regardless if I'm breaking or just cruising to a stop, meaning the brake system's vacuum shouldn't be a problem?
  • When idling or normal driving at constant speed, RPMs are stable.
  • RPM's fluctuate in this and only this window regardless of the outside and engine temperature.
  • There are no DTCs or any other problems with the car.

Service info:

  • Oil and oil filter changes are made on 10.000-13.000km interval w/ Castrol Edge 0w30 A5 and OEM or MANN filter
  • Cleaned Throttle body 11.12.2020 @333.000km (also changed the gasket)
  • Fuel filter 25.02.2022 (MANN) @367.000km
  • EGR clean (not thoroughly, only what I could manage to scrape out) 05.12.2021 @360.000
  • Air filter 23.03.2021 (OEM) @340.000km
  • MAP sensor (Bosch) 11.12.2020 @333.000km

This problem is present since I got the car (2019 @297.000 km). Any ideas?

Volvo s80 2.4D M66 2009 @381.000km

spaceman
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1 Answers1

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I have no experience with Volvo diesels, but VW TDI diesels can have the same issue. They call it "the slow down shudder" and it sounds exactly as you describe. They fix it by slightly increasing the IQ (injection quantity), which is adjustable through a factory-grade scan tool.

For more information, search forums for "slow down shudder" at tdiclub.com or vwvortex.com.

MTA
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