[s-cars] CEL saga - updates

Thu Nov 4 07:31:42 PDT 2010

Have you tested the coolant temperature sensor(not the MFTS)? How are the injectors? 

Wylie Bean
TheRingmeister at triad.rr.com
90 cq
91 90q20v
92 UrS4
08 Q7 3.6
via BlackBerry®

-----Original Message-----
From: "Young, Steve" <sryoung at trane.com>
Sender: s-car-list-bounces at audifans.com
Date: Thu, 4 Nov 2010 10:07:54 
To: S-CAR list<s-car-list at audifans.com>
Subject: [s-cars] CEL saga - updates

I should add some updates here as I had sent this to the list a week ago but it never made it.  In the past week I have:

Checked for fuel in the vacuum line of the FPR.  It was dry, with no fuel odor so I believe the FPR is good.   I also swapped the MAF with a known good unit and thought I had it solved.  40 miles of highway driving with no CEL. Stopped to fill up, and threw a CEL a couple miles after re-starting. Same two codes P0130/P0150, no P1250.

I have been thinking  that it seems like somewhere air is being introduced downstream of the MAF causing the S1 O2 sensors to read lean.  This causes the ECU to richen the mixture which results in my crappy mileage.  Maybe the codes are just a byproduct of the mixture being funky??

I'm thinking the next step is to do a smoke test on the vacuum lines to see if I have a vacuum leak??

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.

Regards,

Steven Young, CEM, CEA
Project Developer - Connecticut / New York / Vermont District
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