M50tu Engine Shudder

[Grey Dog]

Hi all, lost my last post, sorry if duplicate:

I have an engine shudder that occurs at most rpms, with slightly more around 2200 rpm. Problem occurs same w/hot or cold engine, slightly worse in warmer/wet weather. Idle is relatively fine stangely enough. No difference when in or out of gear, either clutch in or out. no fault codes stored, no check engine light ever.

Recently replaced parts are: all 6 coils w/Bosch units, lower t-chain tensioner, vanos solenoid w/plunger, motor mounts, spark plaugs (not fouling or carbon), relatively new fuel and air filters. Injectors were cleaned 6-8 months ago by dealers, piston tops look fine. Also, water pump and fan clutch, as well as alternator. UUS tranny mounts added too.

Dis-connecting the harness connector for the vanos solenoid seems to reduce shudder somewhat, no where near good though.

I plan to take in for upper (internal) t-chain tensioner next Monday, I could not get the old one out. Head internals shiny and clean looking though. To my untrained eye, no excessive wear on cam lobes or t-chains or cam sprockets.

Anyone with experience with this issue, please feel free to post thoughts or disgnostic methods to solve problem, dealers and independents shops not much help.

Thanks alot everyone ! I would love to have a smooth engine again !

[Euro77]

check the o2 sensor, it might be damaged or bad even though there is no ce light.
Are you able to keep the rev stable at around 2.2k rpms in neutral? Try this when the engine is warm.

If you have your foot on the pedal stable and the revs are fluctuating around that rpm range it might be the o2 sensor.