Re: Low boost problems -- at wits end -- HELP!

[Colin Hames <cchames@mm.com>]

You said you shorted the connector pins on the WOT switch.  Did you test
the WOT switch itself?

Colin Hames
'86 5TQW
'98 Passat 1.8t

Gisli Ottarsson wrote:

> Gurus:
>
> I recently purchased an '87 5KTQ with 180k miles on clock.  Condition
> is much better than milage suggests.
>
> When purchased, the car had a punctured Michelin-man hose between the
> intercooler and intake manifold.  After replacing this part, the car
> suffers from low boost, which maxes out at 1.1 bar according to
> in-dash pressure gauge.
>
> In troubleshooting this problem I have relied on Scott Mockry's
> excellent Troubleshooting Tips <http://www.sjmautotechnik.com>
> Is this guy *king* or what?!
>
> A list of my experiments follows in the hope that it will benefit
> someone and that someone might spot a hole in my reasoning.
>
>  1) ECU fault codes:
>
>     Test drove vehicle for > 15 minutes.  Wide Open Throttle in
>     third gear.  Performed ECU fault code dump.  Only 4444 was
>     blinked.  Ergo:  No faults were stored.
>
>  2) Does Waste Gate work?
>
>   a) Applied 20 in Hg vacuum to Waste Gate.  Waste Gate held the
>      pressure.  Ergo:  Diaphragm does not leak.
>
>   b) Quickly removed vacuum.  Heard an audible "CLUNK".  Ergo: Waste
>      Gate is not stuck open.
>
>  3) Does Waste Gate Solenoid work?
>
>     Connected vacuum gauge to the hose that connects WGS to WG.
>     Unplugged Throttle Switch Connector and shorted two lower
>     connector pins.  Observed large swings on vacuum gauge.
>     Ergo:  ECU is speaking to WGS.
>
>  4) Multi-function temp sensor defective?
>
>   a) Based on experiment 3) I conclude that pin 2 is not sending false
>      ground to ECU.
>
>   b) Coolant temperature gauge holds steady at midspan.  Over-heat
>      warning symbol is ordinarily off but proved itself to be working
>      during a near overheat incident.  Ergo:  All seems well.
>
>     Are there other tests available for Multi-function temp sensor?
>
>  5) Does Air Temp Sensor work?
>
>   a) Disconnected ECU and measured resistance across sensor.  I
>      measured 500+ ohms at ca. 77 degrees Fahrenheit.  Ergo: Sensor is
>      good (?)
>
>   b) Reconnected ECO and measured again.  Resistance had dropped to
>      420 ohms.  Ergo:  Sensor has a good connection to ECU.
>
>  6) Vacuum/Boost leak in hoses?
>
>     Connected vacuum pump to two rubber hoses at rear of intake
>     manifold distribution pipe.  Both hoses held 20 in Hg vacuum.
>     Vacuum in one hose caused pressure gauge to read 0.2 bar.
>     Ergo: No leak here.
>
>  7) Problem in Turbo or plumbing?
>
>     I removed turbo cold side intake and turbo exhaust hoses.  Hoses
>     were solid and had no internal obstructions.  No play was
>     noticable in turbo rotors on the axis.  A significant improvement
>     in performance was observed when Michelin-man hose was replaced
>     and boost comes up quicky.  Ergo:  All is well?
>
> I would really appreciate any feedback.  What did I miss?  Where did
> I over-interpret?  What next?
>
> Thanks in advance and thank you very much Scott Mockry!
>
> Gisli
>
> Gisli Ottarsson, PhD
> Mechanical Dynamics Inc.            gisli@adams.com
> 2301 Commonwealth Blvd.             Tel: 1-734-913-2550
> Ann Arbor, Michigan 48105           Fax: 1-734-994-6418