1.6TD bucking \ surging off of idle

[3benny3]

  Smooth throttle increase yields rpm jump of about 400 right above 1000rpm then when coming back down gets the surging which is extremely noticable while driving especially when in 1 or 2 on gravel drive or parking lot. Have tried moving idle, throttle end points and max fuel but no change.

What do y'all think of these causes? https://www.vwdieselparts.com/forum/viewtopic.php?t=9549

Video: https://photos.app.goo.gl/ivNtRWFjL3MpaqY52

[ORCoaster]

I think it would make for an unnerving ride.  How about the pump flange bolts?  Those tight to the engine and the three bolts on the front of the IP are solid and tight?  And then of course there is the last of the bunch of bolts that one on the bottom of the IP.  So many times I catch the face three and forget that one underneath.  I would also crack the nuts on the back of the pump head and reset them just to be sure they are not sending some torque to the lines and back to the pump.  There is already enough of that going on as it is.

Just my nickels worth. 

[3benny3]

 Hey thanks, double checked the IP and mount bolts torque. Pump fells right, no play. Relieved injection lines. May have changed it a tiny bit but don't really think so. Doesn't really run rough so don't believe it's an injector? Runs good on the high end so not fuel supply (and no bubbles).

https://photos.app.goo.gl/uiFbBGyfs7sXOuH23

[RustyCaddy]

Has the pump had it's governor shimmed?

[3benny3]

No, but was going to try that. May still, but just don't ever get close to red line.

Problem Solved: was missing injector mounting bolt that goes on the bracket at the head of the pump (the one that is bolted to the pump with 2 or 3 of the allens that hold the head on). Added that and all is well. I'm not sure I understand how that makes that much difference? But apparently it's there for a reason...

[vanbcguy]

The pump vibrates around effectively changing timing while running. Seems like it shouldn't be a problem but it sure is!

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[3benny3]

 Sure is! Thanks again ya'll

[ORCoaster]

Sorry I forgot to suggest that check as well.  Not normally one that is loose or missing.  But yeah any vibration on the pump seems to matter.  On the lines on some engines as well.  Ya Gotta remember that the little squirt of fuel that is being sent out the back of the pump is not the one that goes into the engine.  It just gets in the line and sends the pressure up high enough to pop the injector.  The fuel used was actually sent there long ago. 

[fatmobile]

That should have come with a vibrating foot too. You can usually feel that in the gas peddle.