[s-cars] Chasing a boost leak -

[calvinlc at earthlink.net]

Have you tried replacing the BPV, or swapping with a known good one?  These
things often go in a way that they cause you to lose a few pounds of boost.
--Calvin


-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Mike Claire
Sent: Sunday, April 15, 2007 12:27 AM
To: S-car list
Subject: [s-cars] Chasing a boost leak -


Gents:  After spending some time in the Home Depot plumbing department, I
figured I'd make short work out of my boost woes.  But, no joy.

The subject is a '93 with a metal crossover, all-metal intercooler, Samcos,
and Pastore 1+ chip.  I'm used to seeing 22 lbs on full boost with my
Autometer boost gauge.  Now it reads more like 16 or 17 lbs, and there are
some new boost-related noises coming from under the hood.

Here's my main question:  If I'm missing 5 or 6 lbs of boost, is that a big
enough leak to easily find when I pressurize the plenum with about 10 or 15
lbs with my compressor?  Because I'm not hearing it.  I figured a 5 lb leak
would be easy to hear.

Now I'm wondering if it's even a leak at all, or if it's the ECU backing off
boost.  I pulled the codes by blinking them out.  Results are inconsistent.
I've seen 2212 (throttle potentiometer), and 2111 (RPM sensor),
intermittently.  I've had no symptoms of problems with these.  I read
everything on Scott Mockrey's site, and ran the Motronic diagnostics (which
includes the throttle pot), no problems.

I've been chasing this issue for weeks now, and sometimes I see codes,
sometimes I get no codes at all.  I'm not convinced the spurious codes are
even related to the low boost problem - for all I know the car's been
throwing codes a long time.  The car's running well, but not perfect.
Occasionally I get slight misfiring under full boost.  I've been suspecting
a weak coil - but who knows.    16 lbs boost is way higher than limp home
mode, so I don't know - can the ECU even be involved here?

One more thing about the codes - I haven't seen any since I replaced the
little rubber tee hose that connects the PCV to the underside of the intake
- it was split wide open.  (I only picked up a pound or 2 of boost after
fixing it.  But the boost needle doesn't flutter anymore).

In general, the car pulls strong and smooth, but boost is low.

So - boost leak, ECU backing off boost?  Or 3rd option - is a failing turbo
a possibility?  There's a weird noise under there between 8 and 10 or 11 lbs
when under WOT.  I can't even describe it, but I pictured a split hose
making that noise.  There are no split hoses.  But the noise is fairly new,
and it's only heard at WOT, when boost is building fast.  I hear the turbo
whistle just like always.



Thanks
Mike
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