89 200 Turbo SAGA goes on ...

LL - NY larrycleung at gmail.com
Tue Jun 7 19:30:43 EDT 2005


One thing to consider while looking for a boost leak would be
to use the "boost gauge" function of your trip computer (see
your owners manual as to how it functions if you don't already
play with it. Just pay attention to the driving while you play with
it if you're on the road, it can be quite distracting!). If the car is
functioning totally correctly, if you are hard on the gas, especially
at higher speeds (such as accelerating up an steep highway hill,
don't know if you have those in Flagstaff), you should see 1.4 on
the gauge and hold as long as you hold the pedal down. 
If the computer is holding back some boost, (don't
recall the all of the conditions for that, although one of these 
conditions is a non-functioning WGV, see previous posts on that)
it'll go to 1.2 and hold.

BUT, if you have a fairly substantial intake system leak (like
a bad MM (ribbed) hose or lower intercooler hose) you may
end up with 1.1 or less, if the leak is QUITE severe, it will have
a hard time staying at 1.0 (which means the engine boosts until
it reaches outside air pressure (1.0 atmospheres), then the rest
of the boost leaks away, but the engine is expecting more). 

Now, two places to check for leaks not mentioned:

1.  Lower Intercooler hose. The large about 3" diameter J-shaped hose
    that runs from the bottom right of the intercooler (radiator
looking thing with
    ribbed MM (for Michelin Man) hose that runs to the top right of
it, directly
    from the engine) to the turbo-charger. They are VERY thick rubber, so they
    can sometimes fail, but look intact, and their thickness lets them
fake integrity
    for a long, long time, (like 16 years). When I finally replaced
mine, it was
    cracked through 3/4 the way around, and yet the car still ran (not
super well,
    but it ran). Fixed the car. It's NOT cheap (around $120 about 2
years ago), and
    is likely a dealer only part, but you need to remove yours in
order to find out
    which of the two types your car has. One is three pieces with a hard plastic
    pipe in it, the other is a single piece rubber hose. BTW, this
hose is a pain to
   get to, easiest to get to if the front bumper (easy to remove) and
grille, are
   removed from the car. 

2. The intercooler itself. The intercooler has an aluminum center
section (core) and
    plastic end tanks, which are crimped to the core. With time, the
crimps can fail
   and there is leakage at the end tanks. But, you ask, how can I tell
that air is
   leaking into ... air? 
   Easy, because there is a notable amount of oil mixed in intake
tract air (don't
   really know why, anyone? Bueller?), wherever there are air leaks, there are
   oil leaks. Feel the intercooler on the bottom, especially near the
end tanks.
   If there is oil present, there is likely a leak. 



On 6/7/05, David Conner <conner at cfm.ohio-state.edu> wrote:
> Fay asks...
> "Are you saying it is the Turbo which is not working."
> Hi Fay,
> No, that's not what I'm saying.  What I'm saying is you have a 16 year old
> Audi with a turbo attached to the engine.  Turbos create a >lot< of extra
> of heat and stress under the hood.  Your car likely has multiple problems.
> Maybe a single one is causing it not to start, but there could very well be
> a number of poor electrical connections, etc that are degrading performance.
> Compared to a non-turbo engine there are more electrical sensors, wiring
> and hoses under the hood.  The turbo generates an extreme amount of heat
> which takes a toll on hoses, wiring, plastic, and everything else under the
> hood.  The turbo creates a lot of >pressure< in the air intake system which
> will cause failure of age/heat weakened components (hoses).  The heat
> stress can also lead to a cracked exhaust manifold.  Leaks or cracks both
> result in vacuum leaks which cause poor running or no-start condition.  The
> turbo pressure >will< blow off a hose if a clamp was accidentally left too
> loose.  (A hose clamp could accidentally be left loose by even the most
> competent and honest mechanic, BTW.)  Access to many of these hoses and
> clamps is difficult and some are impossible to see.  Even if you can see
> the clamp, maybe you can't reach it.  A loose clamp may not >look< loose.
> You had a recent timing belt replacement... this would require removal of
> the intercooler and attendant hoses.  One of these clamps that you can
> barely see, let alone reach, may be loose and later the hose blew off.   A
> non-turbo engine does not have an intercooler and does not blow the hoses
> off or rupture old hoses the way pressure form a turbo will.  Another thing
> on the turbo engine which may have been disturbed during timing belt
> replacement is the wiring/connector for the intercooler temp sensor.  If
> the fragile little wires here are damaged they will short out this sensor
> and rob your engine of power.
> Did your car spend years in the rust/salt belt?  If so, this creates more
> problems.  Sixteen years of high underhood temps causes deteriorated wire
> insulation and connectors.  A poor connection on a single sensor is a
> problem.  Cracked wire insulation and hardened rubber wiring connectors
> allow salt to enter and corrode the electricals.  Access to some of these
> sensors and wiring is difficult.  You cannot afford to replace all the
> things on your car that could cause problems in hopes that one of these
> things will fix it.  A methodical approach is needed where a problem is
> narrowed down to it's source and dealt with.
> Let me give an example from recent experience with my own 89 200Q that
> improved performance...
> The real problem which prevented the engine from running was a loose clamp
> on one of the intercooler hoses... one of the clamps that is hard to see
> and difficult to reach.  No doubt it was me who failed to tighten the
> clamp.  When I tested for spark it appeared to be either no-spark or weak
> spark.  I narrowed the problem down to the coil so I removed it to swap a
> known good coil to see if that would help.  It didn't help because my
> >real< problem was a loose hose clamp.  I examined the old coil and found a
> surprise problem which I suspect is common on these cars.  There is a fat
> wire connector pushed on to the bottom of the coil.  I pulled this
> connector and found >way< too much green corrosion on it.  This wire
> connector would be difficult to examine without removing the coil from the
> car, and coil R&R is not easy, so I had never examined it before.  The
> rubber connector boot here is supposed to seal out water but was hardened
> from old age and no longer doing it's job.  I cleaned up the corrosion,
> smeared di-electric grease around the rubber bootie and re-installed it in
> the car.  Still no start.  Then I found the loose hose clamp and tightened
> it.  Now the car not only starts and runs, but it starts and runs much
> better than before.  So... I had two problems... one which prevented the
> engine from running at all (loose hose), and a second one which caused weak
> spark and reduced performance.  In the end I didn't install a single new
> part, but having some known good spares to swap was a big help. I also had
> plenty of time to troubleshoot at my leisure since I have a spare car to
> drive at all times.  Replacement of the coil with a new one, a $200-250
> part, would also have fixed the weak spark.  If I had paid a competent
> honest mechanic to fix my weak spark I would expect it to have cost at
> >least< $300, maybe a lot more.
> HTH,
> Dave C.
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