Re: '88, 80 Quattro, fuel probs. long

["A. D. Morris" <allanm@primenet.com>]

> From: "Tilden, John" <tilden@data-io.com>
> Date: Thu, 06 Jun 96 09:59:00 PDT
> Subject: '88, 80 Quattro, fuel probs. long
> 
> So lets see if I can get this right:
> I'm working on Tess's '88 80 Quattro, you may have already seen our
> hasty post from last night, sent in panic mode!
> 
> Tess's Quattro has developed a nasty habit.
> It Starts and runs OK when cold, but after warming up, it starts fine,
> but will not run above 1200 RPM!
> 
> Other symptoms:
>      1. Temperature Indicator in Instrument Cluster, seems
>      intermittent!

Mine is too, I doubt that is it, and that sensor is separate from the 
two which feed the ECUs.

>      2. After additional driving, the car will start it's bucking,
>      will run  and pull
>      the car at idle and below 1200 RPM. Above that the Engine cuts
>      out  until the RPM drops below 1200 when it will run again, at low speed.
> 
>      3. Disconnecting the Pressure Regulator (differential P.R.) on
>      the Fuel Control Unit  (KE3 style) the car will run fine in all
>      modes.

Hmmmmm.....Interesting.  The DPR richens or leans the mixture set by 
the mechanical air flow plate.  The DPR is based on ECU signals, and 
I have not seen one make enough difference to cause a problem.  I 
also have not had a bad temp sensor....see below

> 
<<<<<<<SNIP>>>>>>>>> 

>      7. The Temperature Sender looks OK, resistance cold, approx.
>      4Kohms, Hot, 500 ohms. medium warm, 2.5Kohms.

My Temp sensor graph in the Bentley indicates:

Degrees C            Ohms
0                           5 - 6.5K
20                         2 - 3 K
50                         700 - 900
100                       175 - 210

This says your temp sensor is dead.  I appears that this is the 
PROBLEM!!  When the car gets hot, the temp sensor says it is VERY 
cold, and needs a VERY RICH mixture.......

Your car has two sensor with 4 outputs (I think).  Are you measuring 
the one on top of the block, in the radiator hose elbow?  Each of the 
connections to ground?  One  connection is for the FI ECU and one for 
the ignition ECU.

> 
>      8. Slight sign of fuel weeping from the connector on the housing
>      of the 
> 
>      Differential Pressure Regulator. i.e., Red fuel residue.

Look carefully while the car is running, hold a clean towel under it 
and see if it gets wet.  Mine leaked for a while, I filed the DPR 
slightly, replaced the O-rings, and now it doesn't leak.  CAUTION!!  
The DPR is under pressure, and removing the two screws cause gas to 
spray under high pressure!!  (Now how does he know this ? ;)

> 
>      9. Computer diagnostic codes indicate checking the Temperature
>      Sender, and it's wiring.
> 
> So what you all think? Anyone have a similar problem with your '88 or
> later 80/90 Quattro? I will order a new Temp Sender, but I don't think
> it will fix the problem!
> 
> John Tilden
> tilden@data-io.com
> 

If your data is correct on the temp sensor, it should fix the 
problem....

-----------------------------------
A. D. Morris
Phoenix, AZ
allanm@primenet.com
1988 90Q
-----------------------------------