'91 200Q Problem - Wastegate Valve

[Phil@isham-research.demon.co.uk (Phil Payne)]

In message <0a92a2310001297UPIMSSMTPUSR04@email.msn.com> JoMi@msn.com writes:

> I'd be very interested to know how to check the proper operation of the WGFV
> via onboard diagnostics on a 91 200q. Spec is 25-35 ohms and even that is
> not a good measure if it is leaking.

The technique is similar to that used for dumping codes from the ECU.

You will either have a fuse-holder in the top of the fuel pump relay,
or a set of contacts in the left foot well.  In the former case, output
is via the engine warning light in the dashboard, and in the latter case
a diode test lamp has to be attached.

The difference is that the fuse is inserted/contacts bridged _BEFORE_
the ignition is switched on.  Each four-second bridging advances the
diagnostics one step.

On a CIS (10v) system, the fuel pump is started first followed by the
other components.

On a Motronic (20v) system, the injectors are tested IN THE FIRING ORDER
- they're very quiet, so make sure there's no extraneous noise.  Open
the throttle and close it - the closing of the idle switch triggers the
Motronic to fire the injector.  After the fourth test, it switches to
the next injector.  After the fifth injector has been tested, it then
switches to the idle stabiliser valve and everything else continues as
with the CIS system.

The wastegate frequency valve is one of the loudest components, ticking
on around a 1-second cycle.  There's no time limit on this part of the
tests, as there is with the cold start valve.  It's long enough to see,
with a carefully operated Mity-Vac or similar, whether the switched-off
side is holding vacuum reasonably well.

It doesn't really matter if the valve leaks just a little.

Another way to test the wastegate frequency valve is to put a boost
gauge between the valve and the wastegate.  Normal output is a
high-frequency mix of boost and vacuum - the gauge's pointer will be a
blur and you'll probably break off the test run in sympathy for the
gauge.

--
 Phil Payne
 phil@isham-research.demon.co.uk
 Phone: +44 385302803  Fax: +44 1536723021  CIS: 100012,1660