Bad Vibrations

Joseph VanZeipel vanzeipel at
Wed Jun 12 18:06:18 EDT 2002

You may or may not remember my "failed motor mount" last week which
sounded more like a failed intake hose.  It was sparked rather suddenly
when passing at 65 in 4th gear on the highway.  Here are the symptoms
- vibration, heaviest when starting from a stop, not there when
deceleration with engine only (no braking), and is there when idling
- decreased MPG,
- just fixed a broken part in the crankcase breather hose, where it
attaches under the black metal intake tube, after the valve.  Car ran
fine after I fixed this before all this happened.
- I do have a K&N cone filter on there, but I have yet to clean it and
re-oil it since I got it last fall.
- I still get full boost!  1.8 bar cpu indicated.  Gets up to 1.7 pretty
quick (w/in a second of WOT) but 1.8 takes another few seconds to reach
@ 1,300 feet.
- may or may not have some vacuum leaks to chase down.

Well, the weather finally cleared up so I can work on the car (I envy
those of you who have a garage, poor college types like me can only
imagine).  Start up the car after it has been sitting for a few days
(maybe the Audi Gods will be nice and make the problem go away...) but
it still shakes.  I open up the hood and take a look around.  The motor
mounts seem fine  I poke them and they seem to be stiff and responsive.
First thing I pull is the MM hose -- fine.  I then take apart all the
intake tubing down to the turbo inlet -- all fine.  Some slight oil
coating and fine dirt, but no rips or tears or anything of the sort.
Kinda cool having the turbo right there, easy to turn the blades by hand.

Put it all back together, maybe something was loose.  Nope, still
shakes.  I tried disconnecting the crankcase breather where it was
previously severed, maybe I caused the problem by fixing an earlier
problem?  Nope, still vibrating just as hard.

I pulled and inspected the upper intercooler hose (the MM hose right?),
the upper turbo hose, and checked the lower turbo to intercooler hose by
hand.  All seemed fine,  The lower hose has quite a bit of dirt on the
back side of it, but wasn't brittle or soft at all.  I felt the
crankcase breather hoses back behind the engine block and they were
pretty soft in a few places, so that would be my only indication of a
failed hose, but according to SJM's site, a leak here won't cause the
shaking I'm seeing.

What else could it be?  Fuel delivery?  Any insight much appreciated.

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