90 200tq 10v - Total loss of electrical power and bucking
Brian K. Ullrich
bullrich at ullrichsys.com
Sun Nov 22 13:39:20 PST 2009
Thanks for the info. This is a wealth of good diagnostic material. While I
did fix the power issue (bad ground connection on the battery, and I will
add your suggestions), the car does have an idle issue. At operating temp,
the idle RPM degrades until it stalls. To date, I have replaced the plugs
and fuel filter. Air filter is a K&N and clean (my wrench does not like
K&N's. Says it may be a source of air starvation at low RPM. I may switch to
a Mann paper filter). I have not addressed the wires, but I certainly will,
and will service the rotor and distro as you mentioned.
The buck is indeed rather dramatic. Of course, that could be my own
perspective, but it happens at 1.7 bar (indicated), and stops once bar is
under 1.6 (indicated). I occasionally see 1.9 bar (indicated), but it only
fleeting. So.I must have the 1.8 bar chip as you mentioned. Taking your
advice, the first place I will look is the lower WG hose. If it is anything
like the rest of the rubber on this car, it is rotted.
Vacuum leaks will be my next target. I will advise what I find.
Thanks for your advice.
From: Ben Swann [mailto:benswann at verizon.net]
Sent: Sunday, November 22, 2009 1:30 PM
To: bullrich at ullrichsys.com
Cc: quattro at audifans.com; 'Ben Swann'
Subject: 90 200tq 10v - Total loss of electrical power and bucking
Regarding loss of power - If there is absolutly no power to anything, even
before turning the key, then go to the source - the battery located under
rear seat and check, clean terminals and ground strap connection to the
chassis. I'll often wire in a second ground point and strap for
redundancy, sinc this a the single point of failure to the battery.
Also, you have positive connections at the starter and alternator. There is
a single point of failure ground strap that goes from chassis to engine -
located on drivers side engine mounting. Add second strap on the other side
fro redundancy - starter bolt to chassis is a good location.
Several models incl. type 44 have a welded wire connection in harness in
certain locations, but I wouldn't go there unless all else is ruled out.
If the battery went dead due to lost charge, then you may have a bad voltage
regulator or exciter wire disconnected. I bet you find all sort of wiring
that need cleaning up when you go through things.
If the "buck" is rather dramatic, you may well be hitting the overboost fuel
pump cutout - several chips are programmed to cutout at 1.95 bar, but you
may not see that since often the digital readout responds far to slow to
register before it happens. We can assume ti is a 1.8 bar chip, as stock
would have cutout at 1.5 bar and you would have seen maybe 1.3 bar at the
time of cutout.
Cutout usually is due to a bad lower wastegate hose. They get porous and
look ok, but come apart when removing - just replace it if you haven't.
Wastegate diaphragms can leak, but usually not the problem. Any of these
culprits tend to creep in and get progressively worse until repaired.
It could be other things - either ignition or fuel related. Rule out
ignition - plugs, wires, cap and rotor - usually can get by for diagnosis
by cleaning up cap and rotor contacts with emory file or even better if you
have a dremel tool use a small fine wire wheel to clean contacts as I bet
they are covered with green/white oxide. Replace lugs as a matter of course
if needed. Sometimes you can readily tell a wire is bad by observing engine
in pitch dark - amazing the fireworks set off by bad wires. They can be
tested - 1k ohm for plug wires and 4 k ohm for center wire ( hope I got this
right - ref. Bentley. If ignition is still suspect, coil assembly can go
You may have a clogged fuel filter, but not the first thing to replace.
Injectors can get sloppy, but usually associated with poor low RPM and idle.
Vacuum leaks - sometimes can be major - check, replace and repair lines as
This answer will be put into the online Frequently Asked Questions section
of my website:
[Date: Sun, 22 Nov 2009 11:42:30 -0600
From: "Brian K. Ullrich" <bullrich at ullrichsys.com>
Subject: 90 200tq 10v - Total loss of electrical power
To: <quattro at audifans.com>, "'v8audi'" <v8 at audifans.com>, "'200q20V
mailing list'" <200q20v at audifans.com>
Message-ID: <73A7D7194FDC4EF9A162C5A5E95C36D2 at nick>
Content-Type: text/plain; charset="us-ascii"
Update on my '90 200tq project. I got everything back together underside and
the car is tight. Runs well, but has a weird buck at 1.7bar. Also, seems to
idle a little rough and probably rich as it failed an emissions test this
morning. All that is minor right now.
The REAL head-scratcher is that on the way back from the inspection station,
I stopped at a convenience store, and when I came back out, there was no
electrical power in the car at all. Turned the key; nothing. No accessory
power, no lights, nada. It is like there is no battery in the car.
So, the car is stuck at the store, my shop manuals are behind locked doors
at the wrench's shop, and I'm stumped. Any ideas?]
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