Re: Help for Sick Ur-Q

[steveb@falcon.kla.com (Steven Buchholz)]

> got sick.  Yesterday could only get 6 psi of
> boost instead of 16psi.  I tried to diagnose
> the problem last night and came up with plugged
> cat.  I had it changed today for $190.00 and I
> can now get 8 psig.  Still a long way to go.
> 
> Other things I have checked.  The O2 meter reads
> 0.85-0.9 volts on full throttle.  The idle drops
> when the dip stick is pulled.  No visible pressure
> leaks in the system, no responce to propane testing.
> Plugs are a medium brown colour (tri-tips).  Starting
> is good and it pulls evenly, just not strong.  Back
> pressure test at mulffler shop shows low back pressure
> with 5k rpm on lift.  Any more clues or tests would
> be appreciated.  Hope to make it to VC! :-}
> 
... sounds like bad news to me ...

Do you know if your wastegate is opening prematurely or has 
failed?  The only other thing it could be is the turbo.  The
Bentley troubleshooting technique is fairly simple, hold 
constant speed (actually RPMs) in second gear using brakes 
at WOT.  Wait a few seconds ... if the boost isn't at spec 
the turbo is bad.  Wish it were as simple as that!

If you can hit 5k RPM then the ECU is at least passingly 
happy with the input signals, but you might want to confirm 
idle and full throttle switches work and that the intake temp
sender is working (could H2O injection have screwed it up?)
If the timing is right, you're running out of possibilities ...

Good luck Paul!
Steve
s_buchho@kla.com
San Jose, CA (USA)