[s-cars] Chasing a boost leak -

[Theodore Chen]

disconnect the wastegate and see how much boost you get.  that will tell
you very quickly whether you have a boost leak or not.

-t.

--- calvinlc at earthlink.net wrote:

> 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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