[Biturbos4] Fw: Detecting "limp" mode?

Brandon Rogers brogers at terrix.com
Fri Mar 14 07:59:33 PDT 2008

New plugs got rid of my random misfires.  My car is chipped.

'01 S4
'84 ur quattro 20Vt

-----Original Message-----
From: biturbos4-bounces at diablo.audifans.com
[mailto:biturbos4-bounces at diablo.audifans.com] On Behalf Of j y
Sent: Thursday, March 13, 2008 10:16 PM
To: biturbos4
Subject: [Biturbos4] Fw: Detecting "limp" mode?

----- Forwarded Message ----
From: j y <jimnetpa at yahoo.com>
To: Chris Newbold <chris at newbold.org>; quickaudi at gmail.com
Cc: biturbos4 at www.audifans.com
Sent: Friday, March 14, 2008 12:13:13 AM
Subject: Re: [Biturbos4] Detecting "limp" mode?

Since you are not a chipped car and you are getting random/multiple
cylinder misfires. I strongly suggest that you look at your coil-packs
and spark plugs. That's the first suspect on chipped and non-chipped
cars, especially a non-chipped car. My mechanic said that the Bosch
coil-packs on S4s are usually good for about 85-100k before they start
acting up. I was lucky and got over 100k on the original (i.e. "stock")
coil-packs with my Stage 1, 2, and 3 S4, but I definitely picked up
random misfires with VAG. 
My mechanic said that this was a combination of the mods (X-chip, RS4
MAF, K04s, larger injectors, etc.) and my S4's age (MY 2000, production
year 11/99). Personally, I've only gone into (throttle cut induced)
"limp mode" as a result of over-boosting (20+ psi) and when the torque
converter on my tip tranny died ("tranny limp mode", which is possible
on a tip). My S4 has never gone into limp mode under normal (9 psi or
less, which is the stock boost level on a non-chipped S4) boost
Also, if you have an early S4 (MY 2000, MY early 2001), you should also
replace the ignition amplifiers on top of the air-box (if they are the
original (i.e. "stock") set), there are two. They are also known to
cause random/multiple unexplained mis-fires along with coil-packs. When
you change your coil-packs, be sure to put in new spark plugs.
Good luck with your diagnosis.

- ----- Original Message ----
From: Chris Newbold <chris at newbold.org>
To: quickaudi at gmail.com
Cc: biturbos4 at www.audifans.com
Sent: Thursday, March 13, 2008 11:10:06 PM
Subject: Re: [Biturbos4] Detecting "limp" mode?

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

>  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.

2001.5 S4 Avant 6spd _______________________________________________
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