[urq] stumbling under boost

[Eric Renneisen]

Hi Gary,

Here's something to consider: My car used to have a little roughness at
WOT/full boost--not really a stumble, but just a little misfire.  I
resolved it by adding a relay for the fuel pump under the back seat so
that the pump gets a good 12V direct from the battery.

Eric R.
'86 urq
'92 urS
'93 urS

-----Original Message-----
From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On
Behalf Of Gary Brown
Sent: Saturday, June 07, 2008 6:22 PM
To: DGraber460 at aol.com; a.sigal at bluewin.ch
Cc: urq at audifans.com
Subject: Re: [urq] stumbling under boost


I found a possible culprit-
the small PCV hose that is situated below the vacuum
"T" was loose. Removed it and plugged it with my thumb
while I pumped in about 30lbs of air. (I disconnected
the ECU hose and plugged that fitting).
When I let my thumb off the PCV hose fitting, there
was a large "whoosh" of air escaping. No leaks in that
part of the intake system. 
Hooked everything back up, and it's still doing it.

Other ideas? Could it be ignition or pre-turbo vacuum
leak related?

Gary



--- DGraber460 at aol.com wrote:

>  
> In a message dated 6/6/2008 8:03:35 P.M. Mountain
> Daylight Time,
> a.sigal at bluewin.ch writes:
> 
> My 85  urq runs great, except it has developed a
> nasty
> >stumble at full  throttle and full boost.
> >
> >Can't find a vacuum leak and duty  cycle readings
> seem
> >to be correct.
> 
> 
> 
> Sounds like classic boost leak. Turbo over-boosts
> due to lack of  resistance,
> and ECU shuts off the fuel pump.
> If you don't have one make a pressure tester out of
> ABS pipe and a cap  glued 
> together and clamped into the turbo intake. Drill,
> tap, and install an air  
> fitting into this "plug". With this you can
> pressurize the system and with a  
> stethescope check for pressure leaks. Careful not to
> pressurize more than ~  
> 10-12 psi or you risk blowing your pressure
> transducer in the ICU. To be ultra  
> safe, isolate the ICU "just in case".
> Bet you a beer you find a leak (or 2). Even small
> leaks that vacuum  will not 
> betray will be quite obvious.
> Come out in August and I'll either collect or pay
> up!
>  
> Dennis
> Denver
> 
> 
> 
> **************Get trade secrets for amazing burgers.
> Watch "Cooking with 
> Tyler Florence" on AOL Food.      
>
(http://food.aol.com/tyler-florence?video=4?&NCID=aolfod00030000000002)
> 

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