B5 S4 No start

[Mark R]

But when cranking, SHOULD the MAF show airflow?  I suspect that showing zero
is normal.  I always use my VAG-COM, but I know people pull the MAF wiring
to force the car into a limp-home map and see if that makes a power
difference.  Quick and dirty "failed MAF" test.  Any car I see, the MAF is
weak, and not totally failed.

Knowing that the ECU has some fail-safe mapping, I suspect during starting
it ignores the MAF input.  But I can't find any definitive literature on
this in either Bosch or Bentley manuals.

And for an engine like a modern Audi to not start due to an intake leak...
that would be the mother of all intake leaks!  The CIS and CIS-E cars had a
lot of airflow resistance, causing those big rubber hoses to really open
up.  A MAF has negligible resistance and most of the air intake is hard
plastic these days.  The car has all Samco hoses and a bi-pipe and I'll
check the bypass valves as well.

As an aside, surprisingly the car ran OK with an open pressure fitting.  The
turbos were probably over-spinning, but the previous owner who rebuilt the
front end (only needed body work and a radiator) failed to notice the open
plastic fitting under the hood.  The car had a boost gauge plumbed in, but
taken out at some point (after the accident before the insurance company
towed it away, I'm sure).  I fixed that when I repaired the MAF wiring for
the previous owner.

Thanks!
Mark Rosenkrantz

John wrote:
A big vacuum leak comes to mind.  If the MAF isn't passing any air, it ain't
gonna give you a reading.  John