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Re: 91 200q stalls/loses boost
Sounds like you are getting air in the system that is not going past the
Mass Air Flow sensor. Check the Crank Case Breather Hose. The vacuum hose
you replaced from the turbo bypass valve ends up on the drivers side on the
back of the intake manifold - this holds the bypass valve closed when under
boost. My 91 200q would stall in similiar conditions because that hose was
burned thru behind the heat shield. Make sure the hose is not crimped where
it comes out of the IM. Peter had a stalling problem caused by the turbo
bypass valve - is yours installed correctly and are you *sure* it is good?
I would look in this area for the problem - unless the mass airflow sensor
has gone bad.
> From: Sargent Schutt <firstname.lastname@example.org>
> To: Quattro List <email@example.com>
> Subject: 91 200q stalls/loses boost
> Date: Tuesday, May 13, 1997 6:42 PM
> Doctor, doctor, gimme the news...
> Thanks to some ham-fisted mechanics (no, not me this time) my car (91
> 200q - TAP chip/spring, etc) now stalls after being pushed hard - e.g.
> you stand on it to make a light, as you approach the light to take a
> corner or stop, clutch in, the motor will allow itself to stall.
> The problem arose after replacing the vacuum line (had small leak) that
> runs from the turbo cut-off valve to somewhere behind(?) the engine.
> The funny thing is, the check engine light will come on before it
> actually stalls - so probably not the idle stabilizer. Sometimes the ISV
> will compensate, sometimes it canít. I also checked/replaced the turbo
> cut-off valve and that is not the problem. There are no evident vacuum
> leaks, though the problem would seem to be in the vacuum system.
> Also, Part II of this problem (probably related) is a loss of boost
> after 5000 RPMs. It will make it to 1.9 bar, then fall off to 1.8, 1.7
> sometimes 1.6 as redline is approached. The turbo cutoff switch
> registers fine. Iíve seen readings as high as 2.0 - just prior to taking
> it in for the repair!
> Part III - also related I think, throttle response at low RPM in 1st/2nd
> feels more sluggish than before, as though the engine is running rich.
> Might this be electrical (chip?) or vacuum related? It would seem that
> it would be vacuum related as the problem arose out of the replacement
> of the aforementioned vac hose.
> Please help, this stalling stuff has got to end! (not to mention it
> should be going faster!!)
> 91 200q (sputtermobile)
> 86 5ktq (laughs at sputtermobile with throaty Borla grin)