200 10V stumbles, poor mileage

[Ben Swann]

Steve,  Konstantine,

The Cold Start valve only pulses in order to get the engine started, and therefore is
only activated during cranking and possibly initial startup.  The CSV only pulses about
10 times when engine is stone cold.  Any more and the engine would flood quickly.

The CSV does not activate during WOT and not only is not the type of injector that would
be used for additional  fueling, but is in a bad location for adding fuel for
performance - too much fuel would end up at cyl. #4 & 5 and #1 & 2 would be too lean.
So don't consider this location for supplementary injector, which should be placed
before the throttle body or directly in muli-port configuration.

If faulty CSV operation is suspected (I'm scepticatal) then get engine started and
disconnect the connector to it.  Unless it actually is leaking, then CSV would be out of
the picture for diagnosis.  I bet there is no difference and problem lies elsewhere.  If
CSV leaking is suspected, then unbolt it from the manifold and run fuel pump.  You would
see it dripping fuel.

Unless there is visual evidence of a hack job, or melted wiring inside the harness, I'd
be looking for the problem elsewhere.

The sypmtoms as described are that of massive air leak that opens up under load. 

Also, bad temp sendor or O2 sensor would cause problems as described as well as other
culprits.

Once again,  there should not be a path to ground at the CSV connector during normal
engine operation.  If engine is not running, but ignition is on, I surmise that the loop
would be closed and perhaps that is why it is suspect.  Check while engine is running -
should be no continuity to ground.

Ben


[Date: Sat, 2 Jan 2010 00:44:55 -0800
From: "urq" <urq at pacbell.net>
Subject: Re: 200 10V stumbles, poor mileage
To: "'Quattro List'" <quattro at audifans.com>
Message-ID: <00be01ca8b87$dba9bae0$92fd30a0$@net>
Content-Type: text/plain;	charset="us-ascii"

I spent some time reacquainting myself with this one by reading some of the messages to
date and pulling out the Bentley.

The patient is a 1991 200, 10V with MC-2 engine, correct?  I did not find a direct quote
of this, but inferred it from tidbits here and there, so I wanted to start here ... 

The problem is that the engine runs poorly below 3000 RPM, but seems to recover above
that speed.  I don't recall seeing anything about ECU codes, do you get any codes while
the engine is running?  Have you read them while the engine was malfunctioning?

The current suspicion is that the cold start injector is running when it should not be;
this being borne out by measuring the voltage across the terminals to the CSV.  The
power (12V) is supplied to pin 2 of the CSV via the Blu/Blk wire which is ultimately
connected to the fuel pump relay.
Seeing +12V at this terminal while the engine is running is expected behavior (that
said, you should not see +12V when the engine is stopped, even with the ignition on).
Terminal 1 of the CSV goes to pin 1 of the ECU via a Blu/Red wire.  This pin should be
at ground only when the ECU wants to add extra fuel via the CSV.  I don't have the
detailed functional description of the ECU, but I'd expect this to be when cranking the
engine (cold and hot), and perhaps in certain cases of high boost (I don't know this for
a fact).  I would *NOT* expect to see the CSV activated on an engine that was running at
or near idle or below 3000RPM with light load.
It sounds that perhaps the ECU has been replaced for a similar condition in the past, is
this true?  I'd recommend that you verify that there's not a short to ground inside the
CSV itself, or in the wiring harness between the CSV and ECU before trying another ECU.
I'd be very skeptical that it would be some sort of hack from a PO ... unless you have
seen some other "performance improvement" hacks in the car.  

All this said ... do you know for a fact that the CSV is the source of your poor
performance?  A simple test of this hypothesis would be to unplug the CSV while the
engine is running and see if the performance improves.  If it does not, the CSV is not
the source of your problem and we should start looking elsewhere.  

Good luck on getting this nailed quickly!
Steve Buchholz

Happy New Year and all the best for 2010 to all the audifans!

-----Original Message-----

That what I thought how it should work. But there is 12V across the connector when car
was running for awhile (and was hot). Can someone test it on a running car? :) I recall
from long time ago that other people reported that CSV was engaged well after cranking. 
-- Konstantine 

----- Original Message -----
From: "Ben Swann" <benswann at verizon.net> 

That does not sound right. 

The injector should pulse during startup when the engine is cold. Duration of pulses is
dependent upon engine temp. The pulse is caused by a switching to ground AFAIK - either
through the ECU or some other means - depending upon ECU. 

There should not be a constant current path on both side of injector terminals. There
would be a positive voltage present on one terminal all times and shared with other
devices (blue/black wire), but other terminal should not go to ground except through the
ECU(pin 1). 

That is the way I recall without looking in more detail at the manual or other
schematics. 

See http://www.gtquattro.com/MCWiring.html for wiring details - MAC-14 is similar. 

Ben ]