5KTQ wierdness...

[Ned Ritchie]

Stephen,

1st I assume what you have is an air/fuel gauge which is really an
oxygen sensor that is calibrated in air/fuel.

2nd  These are ONLY meaningful when all systems are working properly.

3rd  If the first assumption is true then you have an excess oxygen
situation only, and you must completely throw out any air/fuel stuff
until you determine what is really going on.

3rd  In this situation I assume an engine misfire.  Plug, Wire, Coil,
low voltage, or whatever. (This is a textbook case where O2 sensor is
reading lean "?", but the engine is running rich because of the O2
sensor.) 

EXAMPLE:  If you have one cylinder missing ALL the oxygen leaves that
cylinder and is read by the O2 sensor as EXCESS OXYGEN.  (In a properly
running engine meaning LEAN, but in this case a WRONG interpretation)
In order to correct the situation the Audi engine management system
attempts to add more fuel which makes all cylinders run rich.  What a
mess is now created.  In the meantime the Air/Fuel Sensor is screaming
LEAN, LEAN, LEAN.  In reality all it was told was a voltage that was a
result of excess Oxygen.

Someone behind in another car may watch black smoke indicating the TRUE
situation created by the first engine misfire.


Ned Ritchie

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com]
On Behalf Of Stephen Ankney
Sent: Wednesday, July 07, 2004 11:03 PM
To: quattro at audifans.com
Subject: 5KTQ wierdness...

Hi,

My 5ktq has developed a bad attitude lately.

At WOT at around 4,000 rpm's it goes from rich to way lean and is way
down 
on power.

I monitor this behavior with a A/F gauge. I know this isn't too relaible
of 
a way to monitor my fuel supply but I can feel the car retarding the
timing 
so I know something is amiss.

I first noticed the behavior as I was blasting down a highway onramp. I 
noticed the instrument cluster flicker and then watched as the A/F gauge

instantly dipped into the red indicating a lean condition and the engine

felt "underpowered". I thought this was strange so I repeated a couple 
morepulls with the same behavior from the A/F gauge. The cluster did not

flick anymore but right before I got home it went completely out and
then 
came on? Like I said, strange.

Any ideas? I'm stumped. I'm not sure how any of this could be connected?

I though maybe a shared bad ground somewhere so I cleaned up a couple of

connections and the problem still persists.

The car has a IA chip and still makes 12 psi. There is no overboosting 
problem. That was the first thing I checked.

Any ideas?

Steve

_________________________________________________________________
FREE pop-up blocking with the new MSN Toolbar - get it now! 
http://toolbar.msn.click-url.com/go/onm00200415ave/direct/01/

_______________________________________________
quattro mailing list
quattro at audifans.com
http://www.audifans.com/mailman/listinfo/quattro