[Biturbos4] Detecting "limp" mode?

[Chris Newbold]

On Thu, Mar 13, 2008 at 10:11 PM, Joel Liggins <quickaudi at gmail.com> wrote:

>  Bailey DVs have to be serviced between 15k and 25k miles.  I believe you can
>  find the procedure on their website.  Probably not causing the issue, but
>  couldn't hurt to try.

I'll check it out; good to know that this needs to be done.

>  If you've had the "random multiple misfires" code, then something definitely
>  isn't right.  Those just don't randomly appear.  Is that the code you had,
>  or was it a specific bank/cylinder?

Both, actually. I've got the "random, multiple" code as well as a
cylinder-specific code.

I can imagine how to troubleshoot the cylinder-specific misfires (swap
coil packs, etc.) Any tips on how to go hunting for the
"random-multiple" issue?

>  Random thought: have you checked the brake booster hose that plugs into the
>  accordian hose?  Caused me to run rich and have misfires once.

I'll give it a look in the morning.

>  Are your oxygen sensors stock as well?  (i.e., not been replaced)

Yup; all four are still original. I'm actually surprised that at least
one hasn't gone so far off the map as to trigger a CEL by now....

>  As for a measuring block in vagcom, if you do a 3rd gear WOT run and log
>  block 003, you might see a throttle cut condition (throttle plate should be
>  100% from 4k rpm on), or if you log block 115, you can monitor boost
>  pressure, both requested and actual.

The specified-vs-actual boost graph is pretty much the only one I know
to try. I did a couple of 2nd-3rd gear pulls tonight and the results
didn't look too ratty. Little spikes when lifting and the occasional
one when jumping on the throttle at low RPM. It looked like the ECU
pretty much got the boost it asked for-- no major discrepancy between
the specified level and the actual.

I guess this says that, if there is an issue, it's causing the ECU to
hold back rather than a problem achieving the boost the ECU asked
for...

Thanks for the suggestions.

-Chris
2001.5 S4 Avant 6spd