Re: 5000S Help!

[Alex Kowalski <akowalsk@shrike.depaul.edu>]

> Tom Johnson wrote:
>
> I have recently bought a 5000S, 1985, 2.3 liter engine, 89,000 miles,
> paid $1,600.00.  I've had the car for about 5 months now and have had
> some minor problems with it since.  Well, now I have a big problem (I
> think) and I was wondering if anyone out there could give me some
> advice.  Let me prefice this problem by saying that I am new to owning
> and Audi, I enjoy driving it very much, and would like to keep it or
> buy another.
>
> Shortly after I got the car, I had problems with it stalling and making
> noises from the rear.  My mechanic thought that this was the fuel pump
> and replaced it and the fuel filter.  The car ran without stalling,
> however, noises from the fuel pump were still there at times (which I
> hear is normal for Audi pumps).
>
> About 2 weeks after, the car stalled on me again and was running rough.
> My mechanic looked at it again and said that he couldnt figure out what
> was wrong with it but would talk to a friend of his who works on
> Audi's.  He was told to check the grounds and after doing so the car
> ran fine for weeks.
>
> Then, about 3 weeks ago, the car started idling rough and lacked power
> in the 1000-2200 RPM range, occuring when accelerating from a dead
> stop, or crawling through traffic.  The car ran fine at higher RPM's.
> Then about 4 days ago, the car really began idling rough (sounding like
> it would stall any second) and the sluggishness became worse and
> started to happen over the 2200 RPM range at times.  The only solution
> to get the car moving at a normal speed was to step on the accelerator
> 3/4 of the way down.  If I accelerated normally the car would sputter a
> bit and rev slowly until it reached the mid 2,000 RPM range, then it
> would take off.  The car also had very poor power when going uphills or
> when the a/c was on.  Well, yesterday, the car stalled and I cannot get
> it started again.
>
> I pushed it to my mechanic and he said two things: 1) there is gas in
> the cylinders and 2) the cylinder compression on 4 cylinders is ~60psi
> and on one it is ~30psi.  Note that gas in the cylinders was not
> evident two days ago (I checked the plugs).  Right now we are in the
> process of letting the gas dry out of the engine and seeing if we can
> start it again.  As of today, it will not start.  He is a good
> mechanic, but does not like Audi's much and has not worked on them
> alot.  He suggests for me to get rid of the car.  A little history:
> fuel pump, filter, and fuel distributor are new.  Fuel injector(s) *
> may* be clogged.  Ignition system appears to be fine (but he does not
> have the computer to hook the car up to).  Transmission was rebuilt not
> to long ago and the front axles replaced.  Brakes are good and there
> are no electrical problems to speak of.  Radiator and fan were replaced
> in 1990.  Body and interior are in great shape.
>
> Questions are: 1) Does this sound like I need a new engine or could it
> be something else?, 2) If it does need a new engine, is it worth having
> this one rebuilt, buying a new rebuilt engine, or should I scrap the
> car and look for another Audi?  If I were to buy another one it would
> have to be in the 84-88 year range for financial reasons.  Obviously I
> want to make the smarter choice, but since I am not familiar with
> Audi's I dont know what the smart choice is.
>
> Any advice??
> 

If the exhaust isn't blocked, then you have some problem with the fuel
injection or ignition systems.  As a relatively cheap test, you might try
cleaning or replacing the plugs, drying the engine out, filling the tank
with gas, and swapping the ignition coil.  Perhaps the coil is marginal.
When mine went on my 4000Q, it caused some behaviors similar to the
strangeness you relate, including the eventual non-starting. It was
perplexing because the plugs <seemed> to get spark, but it wasn't
strong enough until the coil was replaced, then it started right up.
Your mechanic might have a suitable coil that you can use for testing
purposes.  I got a clean one from a junk yard (yes, I know, Sacrilege!)
out of a wrecked 4000 that I keep as a spare. Plug it in and make sure
the car is getting spark.

Beyond that, there are many things that <could> be wrong, from the
mundane to the $$$. Since you have replaced the fuel pump and filter,
perhaps there is something in the gas tank that the previous owner
neglected to mention (i.e., a rag floating around inside from having lost
a gas cap) that is intermittently blocking the flow.  If the pump is
getting good fuel supply and the return line isn't blocked, then you will
need to measure the fuel pressure while the engine is cranking/running to
determine exactly where the problem is.

The simple fact that the cylinders are getting wet doesn't necessarily
imply that the F.I. is working right -- a device called the Cold Start
Valve (it is an extra, electronically switched fuel injector, with a
braided steel line running from the Medusa-headed fuel distributor to
intake manifold) is there to inject fuel into the intake manifold when
the engine is COLD.  Your mechanic might try testing that to make sure
that it is, in fact, working and then shutting itself off after the
engine has been cranking for a while.  It is easy to unscrew it (using
metric allen-head wrench), place it in a bottle, and observe while you
crank the engine.  I don't know exactly, but I believe 10-15 seconds is
the MAX it should spray while cranking (cold engine, remove and ground
the main distributor wire).   If it isn't shutting off or is leaking, it
can cause rough idling and poor running at low RPM because the engine
gets too much fuel.

Also, check the obvious - make sure there are no vacuum leaks in the
intake tract. Probably your mechanic has done this already, but it never
hurts to double-check.  You can do this by spraying a <small> quantity of
starting fluid at various points around the intake tract while the engine
is running (be careful!) or, less reliably, by a thorough visual
inspection of all underhood hoses, boots, clamps, unions, etc.

Two other obvious things I can think of:

        1) Remove big, circular end of the rubber boot that attaches the
fuel injection system to the intake manifold (it has a large screw-type
clamp securing it).  Pry it off carefully and look inside.  Verify that
the circular metering plate inside is perfectly centered in the venturi
and the anchoring nut is tight.  Using a magnet or some similar means,
<gently> lift the metering plate by the nut.  It should rise without
friction or binding, but with slight resistance.  Its return should be
smooth and free, and it should fall so that it is even with the bottom of
the venturi.  If not, or it is not centered, the FI system can't meter
fuel properly.

        2) If you can get the engine started, the Idle Control Valve
should be humming.  It is the approx. 1-3/4" diameter cylinder with wires
attached to it that is connected to the rubber inlet tract.  It may be
hard to hear with the engine going, so you may have to use a stethoscope
or the 'ol screwdriver pressed against it and your ear.  If it doesn't
hum, it is either broken or not receiving the proper signals from the
computer.

You say that the engine won't start...but does it at least fire on some
cylinders during cranking? Do you hear the whine of the fuel pump prior
to cranking? (You can hear it when you turn the key from the OFF to the
RUN position).  If not, the fuel pump relay may be bad.  I have seen some
strange behaviors from my car caused by the fuel pump relay.  When it was
very hot last summer and the relay was getting ready to die, it caused
some panic-stricken bewilderment before it finally crapped out.  They are
relatively expensive from a dealer but you may have better luck with an
aftermarket Audi supplier.  Even if it is not bad now, once you get your
car fixed I would keep a spare in the glove compartment just in case.  If
it blows, the engine 'she no go.

Ultimately, if nothing cheap works, you will have to take the car to an
Audi specialist (either a dealer or a reputable mechanic) to get the fuel
injection and ignition systems scoped out properly (i.e., fuel pressure
testing and sensor/computer diagnosis).  It may well be that once this is
done, your problem is still relatively minor.  Have patience and faith,
and find a good Audi mechanic.  The Audi gods are fickle, but only rarely
so malicious as to kill a whole engine after you have just purchased the
car (with relatively low miles, too).

Sorry for the obscene length of this reply.

Best of luck,
Alex Kowalski
'84 4KQ