[Biturbos4] Detecting "limp" mode?

Chris Newbold chris at newbold.org
Sat Mar 15 07:06:38 PDT 2008

On Fri, Mar 14, 2008 at 9:11 AM, Long, Scott G A1C USAF AFMC 88
SFS/S4W <Scott.Long2 at wpafb.af.mil> wrote:

> I would also suggest the coil packs.  You said the plugs are newer so
>  that would mean they aren't getting good spark from the packs.  Also
>  like mentioned look at those amplifiers on the airbox.  I don't know
>  what the part #'s are or the cost on those items though.

Looking at the misfire counts with the engine idling reveals that
cylinders 1, 2 and 3 are all running fine with zero misfires, but 4,
5, and 6 are accumulating a sizable number of misfires. Cylinders 4
and 6 clearly exceed the threshold documented in Bentley for trouble
(count > 15); 5 doesn't but isn't clean either.

Given that all the trouble is in one bank, I'm inclined to think at
this point that it is likely to be the output stage widget (amplifier)
for that bank. I'll do some component-swapping this weekend to see if
that's the case or if it's multiple bad coil packs.

I'm inclinded to just replace everything, but those output stage
widgets are $200 a pop...

2001.5 S4 Avant 6spd

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