[200q20v] Re: Help needed with a 1992 S4 Avant SOLVED

[Mihnea Cotet]

>Technically there are three fuses; ECU, memory for ECU, and a third fuse
>for things like the O2 heater circuit and a handful of valves. Only two
>are for the ECU directly; which is why they're both under a little red
>cover marked "MOTOR"
>
>   It will not cause code reading to fail, because the ignition must be on
> in order to read them during which the ECU gets power from  its main
> fuse; there will, however, not be any codes -if- the memory fuse is
> missing and you shut the car off for more than a few seconds; you will
> get a happy "4444", "all's well!" from the ECU(well, there will probably
> be a complaint about the crank speed sensor since the engine is stopped.)
>
>I suspect that in this case there are missing bulbs in addition to the
>problems, but that there is no code stored. Audi had a lovely habit of not
>installing check engine bulbs unless required to do so; note that Audi
>only started sporting a -specific- check engine light around the time
>California required it.  Only California got the bulb here in the
>states.  You two would know better than I if Europe, for the most part,
>did, but it strikes me that if most of the US never got the bulb, then
>neither did Europe.
>
>It is also quite possible that there simply -isn't- a code to be
>read.  The early ECUs were still pretty "stupid"; my car though a blown
>wgfv the ECU though was a "bad throttle position sensor."  I correctly
>diagnosed it; the PO's dealer did not, and simply replaced the $$$
>position sensor, then never bothered to see if new codes popped up(they
>did, and the car would only hit 1.2-1.3 bar.)  His loss; my gain.  $300
>position sensor for $60.
>
>Usually when someone messes around in that area of the engine bay, they've
>either bumped, unplugged, or disconnected one of three things.
>
>a)MAF sensor- car will idle etc fine but not much more getting going in
>1st and small hills will give you problems :)  Obvious enough to check and
>this will generate a code, instantly.  Unlikely to be the problem due to
>the severity of malfunction it would cause.
>
>b)wastegate frequency valve- car will get about 1.2-1.3 bar, and that's
>it; more if the owner has been messing with the wastegate spring.  The
>20vt never goes into a "no boost" limp home mode; it can only limit boost
>to 1.2-1.3 bar.  Will not always generate a code, and -might- generate a
>phantom code as described above.  Can be checked via the output sequence
>test and via measuring the resistance of the valve; I -think- 300 Ohms is
>standard(check the Bentley to be sure.)
>
>c)turbo bypass valve- if it is broken or the hose to it is leaking(this is
>more common on the 200q20v, not the S4) then the car will stumble or stall
>when coming to a stop at stop signs, traffic lights, end of off ramps,
>etc., and will not get full boost many times, particularly if
>chipped  This is the most "dangerous" of the three, since it puts
>additional stress on the turbo; it is -very- dangerous if the ECU is
>chipped since you run a -very- good chance of overspinning the turbo.  If
>the engine is not chipped, than the stock valve is more than suitable and
>will last quite a long time(60k or more miles; t-belts last less.)
>
>Thankfully the S-cars don't have such a moronic vacuum hose routing as on
>the 3B; I saw eS2 conversion #2 (3B engine used) where the line had been
>replaced with copper tubing the entire length of the run behind the heat
>shield; very smart solution to the problem.  As for the valve, thanks to
>the A4 and S4tt guys, there are now dozens of $150(and up) alternatives to
>the Bosch valves($60-70) but I have heard of problems with some(don't
>remember which, sorry.)  There is a Porsche 996 turbo bypass valve that is
>rumored to be more durable than the extremely common Bosch valve(used in
>everything from early-eighties saabs to our Audis etc.)  It is somewhat of
>a shame that Bosch still hasn't fixed the problem.  I imagine that they
>will, shortly, given the number of S4tts in particular having problems
>with them and overspinning their turbos; same with the 225hp TT.
>Audi/Bosch's own damn fault; they knew the valve was busting in the
>200q20vs and S4/S6's over time.
>
>   If there are no codes stored and the car still gets 1.2-1.3 bar, then
> you probably have an overheat signal being sent to the ECU; the quickest
> check, if it is above 40 degrees F, is to hit the A/C button and see if
> the A/C fires up.  If not(remember it must be above 40 degrees), replace
> the multifunction temp sensor, it is sending a false overheat.

Thanks for your replies guys!

I did the output test procedure and everything worked fine, so we tried to
pull the codes...tried but couldn't do it! Actually his S4 dash doesn't
have a Check Engine light...no problems we say, let's just puta bulb there
and it'll be okay...huh? Diesel prewarming sign between the ABS and the
battery lights!!! No trace of an airbag light and no aircon either! His car
has Autocheck but it doesn't seem to want to run...we just tried to pull
the codes with a led and a resistor in series...I jumped the two outer
connections and put the LED b/w the inner "-" connection (black connector)
and the outer "+" connection and all it did was that the led won't
shut...lit all of the time, even though we did the procedure twice or
thrice....so he'll go and have a dealer put the 1551 on it and we'll see...
What we did when checking the WGFV is that we removed the K&N twin cone
filter from the MAF and I noticed it was oily...just cleaned it with my
thumb and when we went for a test drive, the car seemed to have regained
its power back....nice, I think the only trouble was the oil on the MAF (I
know now, K&N sucks!) that caused an incorrect reading and output from the
MAF...he told me that the car seemed to run way too rich (which has already
happened to fello lister Levent Cur, same symptoms, same results after
cleaning the MAF wires) and used a lot of fuel, even with an
economical  driving style.
When he came back at home, he removed the K&N, put the airbox back, cleaned
the MAF wires with brake cleaner, put a shim under the WG spring (stock
ECU) and he told me that the car was monstruous again, so that was it!

Why don't European S4's even have the Check Engine light wiring? Can't
understand this, it seems that Audi only wanted them to be troubleshooted
with a 1551 type of scanning tool! Bad Audi! :)

Anyway, thanks again for the replies and the help!


Mihnea