[s-cars] {s-cars] CEL saga

[Tom Green]

Steve,

I would look at fuel pressure and vacuum hoses.  Hopefully your  
independent friend can put a gage on it to monitor the pressure.  It  
could be as simple as a fuel pressure regulator or a vacuum leak.

Tom '95 S6
          '95.5 S6 avant
Knoxville, TN

On Thursday November 4, 2010, at 9:03 AM, "Young, Steve" <sryoung at trane.com 
 >  wrote:


> While this isn't s-car specific, any BTDT's could be helpful to  
> all.  I'm looking for any ideas here from the collective knowledge  
> bank.  TIA
>
> First, a little background. I purchased a 1998 A6QA with an "mildly"  
> overheated motor (so I was told) cheap thinking I could do  
> headgaskets and get away with a running car for small money. When  
> you're finished laughing, read on. Anyway, block was full of water  
> and rusted, heads were toast and could not be re-surfaced. Used the  
> block from my 1996 A6Q, and got heads from Shokan. Got the car back  
> together and it runs well. Shortly thereafter, it threw a CEL.  
> Pulled P0130 16514 92-00 B1S1 O2 sensor. Changed the O2 sensor with  
> a known good used one, cleared code. CEL again, same code. Changed  
> O2 sensor with a new one, cleared code. CEL again with code P0150  
> 16534 92-00 B2S1 O2 sensor this time. Changed O2 sensor with a known  
> good used one, cleared code. CEL again with
> P0130 16514 92-00 B1S1 O2 sensor
>
> P0150 16534 92-00 B2S1 O2 sensor
>
> P1250 17658 68-00 Fuel level too low cyl 1
>
> At this point, I took it to a friend who is an independent mechanic.  
> He put a code reader and two scopes on it to check the signals from  
> the O2 sensor, and check the wiring from the O2 sensors to the ECU.  
> Signals good, wiring good. Thinking ECU. Purchased a used ECU from  
> Shokan. Swapped in ECU, no dice, same codes.
>
> I can drive the car around town indefinitely without throwing a CEL.  
> As soon as I hit the highway with sustained speeds of over 60mph, it  
> throws a CEL. Mileage sucks, but that's due to the codes stored.
>
> Since I couldn't drive the car when I bought it, I have no idea if  
> this was an issue for the previous owner or something new since the  
> engine work. I'm stumped, and looking for any ideas. Thanks.