Re: Questions of an ur-Q Kind

[Robert Houk - WorkGroup Server Firmware <Robert.Houk@East.Sun.COM>]

   ... I don't know your service guy, so I'm assuming that he knows ZIP about
   QTCs ... since I don't know him I may be totally wrong of course.

Probably a safe guess!
								    Yes, the
   WX engine is interference, but it would probably take a broken belt to cause
   any destructive interference.  Did he even check the timing between the cam
   and the flywheel?  The F/TCU on the ur-q doesn't allow a lot of variation of
   the distributor sender's timing window, so if it got too far out there's no
   way you'd even get spark.  

   Based on your description I would suspect that the more likely culprit is a
   vacuum leak in the intake tract.

I'll second that.

                                   You probably had a little one before, but
   when the engine backfired it probably made it even bigger.

One that nailed me is that there is a "cork" (not a real cork of course,
just a metal plug) in the backside of the intake manifold assembly; I
took a major backfire that blew the plug right out of the manifold...
you might have dislodged/cracked the plug.

                                                               The hose that
   goes from the dome on top of the airflow sensor to the turbo inlet is the
   prime suspect IME (BTDTxn) ... unfortunately this hose is probably a $150+
   item, even at the Carlsen discount. See if you can get the engine to run
   long enough to feel for suction and try to cover any holes with your hand to
   see if the idle calms down (many times the leaks are difficult to see as
   they look just like reinforcing ribs).  After losing a second one of these

Another test is to pour water over/along suspect areas -- when the water
finds a small leak, it tends to "seal" it and the engine immediate runs
better; larger leaks you will it suck the water in. Some people advocate
using ether (insert favorite highly volatile gaseous substance here) to
spray around the leak -- the effect will be pretty dramatic (ranges from
engine goes Zoom-tinkle-tinkle to fireballs and mushroom clouds) and I
would really strongly discourage this approach!

   on my car I figured that the primary source of the problem was the fact that
   this hose runs fairly close to the turbo, and the heat of the turbo cooks
   the hose and makes it brittle.  When I replaced the hose for the second time
   I fashioned a heat shield from some heavy foil & fiberglass material ... and
   haven't had a problem since.  My recommendation to you if this is indeed
   your problem is to try to find the same sort of hose that Audi used (Graydon
   Stuckey's intercooler => TB hose for MC engines looks similar in structure
   but is too large in diameter) and rebuild your old hose.  Fortunately this
   hose on the QTC is before the turbo, so it really doesn't have to hold above
   atmospheric pressure ... it just needs to be reinforced so that it does not
   collapse under vacuum.  

   There may be some other problem that is causing your car to run poorly, like
   a problem with the ground wire that attaches to the firewall end of the
   intake manifold.  As an ur-q owner it is highly recommended that you get
   copies of the QTC IST (Introductory Service Training) documents ... they are
   available from Dyment Distributions (Dyment can be contacted at
   800.544.8021).  Here is the order information:

   Order #
   WSP 451 556 00 - Audi Quattro Introductory Service Training Manual
   [ur-quattro]
   WSP 452 557 00 - Audi Quattro Maintenance and Adjustments Manual
   [ur-quattro]

If you're dumb enough to own an UrQ, you gotta have those docs! (I've
excerpted/posted a few of the interesting pages/diagrams on my UrQ
page)

   FYI, the former document gives a good overview of the systems of the car
   (engine, brakes, drive train, etc.) ... with a good bit of theory of
   operation, while the latter document describes things like torque specs and
   troubleshooting procedures (like what to do when your fuel pump shuts down
   at 4000 RPM :).  These documents go into such detail as to describe the
   timing and boost maps that are programmed into the F/TCU.  I paid US$10 each
   ... a tremendous bargain IMO.  

   If you want to check for bent valves it is possible that you would be able
   to see the impact points on the piston crowns (I could make them out on the
   piston crowns of the MC with the head off, but I really had to look in a
   couple cases) ... a compression check would be the better method I would
   think.  Here again, I would expect a qualified service person to know this
   and do it without my having to ask if bent valves were the prime suspect.
   I'll put my money on a fairly simple to repair problem though ... good luck
   to you Douglas!

A leak-down test is a good idea, it can tell you a whole lot about the
state of the top-end of your engine. $2200 sounds a bit high for a
"rebuild", although if he replaces everything, I can believe it; I just
wonder if it is necessary. By the way, on a head rebuild, don't let
him "grind" the valves, that will destroy them...

					-RDH