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Discussion Starter · #1 · (Edited)
Hey guys, hoping for some advice/help here.

Did a bunch of maintenance 5-10k ago.
  • motor mounts + snub mount
  • tranny mounts
  • spark plugs
  • oil pressure sensor
  • new calipers, pads, rotors all around
  • fuel filter
  • valve cover gasket

Car is a 2000 Passat wagon 1.8t with 345xxx KMs manual transmission
  • unitronic tune stage 1 since 260k
  • solowerks coils since approx 300K
  • also did control arms, wheel bearings, mounts, ball joints etc at same time as coilovers


Car was/is running flawlessly short of the bucking under deceleration. I'm heading out with wife and baby, on highway, let off throttle and car starts bucking. Quite violently.

Any amount of throttle and it goes away. Pushing the clutch in (to the floor) or coasting in neutral, also no problems.

No CEL, no codes on VCDS lite. Tried unplugging and testing spare ignition coils. But no issues under acceleration, or idle. Tried the old propane trick to find vacuum leaks and came up empty handed.

Replaced an aftermarket axle with a used oe one I've been saving. Passenger side is OE still. Both now OE, but not new. I do have creaking over bumps from the passenger side suspension area. Could it be that axle has gone bad? Was thinking it may have been the strut but it doesn't appear to have any leaks whatsoever.

Thoughts?
 

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Did it start right after any work or did it take time?
Does the engine rev at all when you push in the clutch on the highway or is it steady?
Does the instant mpg reading jump or just show the dashes when this happens?
Instead of propane, try building a boost leak tester. It's possible you have a collapsed/collapsing intake hose, maybe the turbo inlet pipe as they can collapse under high vacuum.
 

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Discussion Starter · #4 ·
Did it start right after any work or did it take time?
Does the engine rev at all when you push in the clutch on the highway or is it steady?
Does the instant mpg reading jump or just show the dashes when this happens?
Instead of propane, try building a boost leak tester. It's possible you have a collapsed/collapsing intake hose, maybe the turbo inlet pipe as they can collapse under high vacuum.
Just happened out of nowhere. Hadn't done any recent work.

Engine does not rev when pushing in clutch, just RPMs drop to idle, as is normal.

I dont think MPG reading jumps or shows dashes. Do not see any change from usual in this.

I will check the turbo inlet pipe. Maybe the crack is small enough that it only affects post-boost?
 
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