[tech] Help diagnosing an 8V?

[m-carlson@comcast.net (Michael Carlson)]

> > setting me straight.  (Interestingly enough, I can hear the valve click
when
> > the engine stumbles...)
>
> Hmmm....I'd have to see why that would do that....

My guess is that the rpms drop low enough when it stumbles that the valve is
tricked into thinking it has to compensate.  <shrug>

> Well there goes my whole theory out the window.  BUT, I would still like
> you to hook up the dwell meter to the test plug and find out what the
> Jetronic is doing.

Looks like I get to buy my first dwell meter tomorrow.  :)  (No more time to
fool around with it tonight.)

> Hmmm....very curious.  When you hit the switch, do you hear the frequency
> valve change pitch?  Sounds like the car is stumbling because the mixture
> IS fluctuating...but might not...the dwell meter readings will be key
> here.

I didn't notice the frequency valve changing pitch.

Here's some more info:  Once the engine is warm, it starts up fine and the
weird idle behavior disappears.  While underway, (again, once the engine is
warm), the roughness appears to be slightly decreased but still present.

I checked the plug wires and they all appear to be fine.  I also checked the
condition of the spark plugs.  Plug #2 was carbon-fouled, but the other
three had normal gray/tan colorations.  I cleaned the electrodes on #2, but
the problem was still present.  That indicates to me that the fouled plug is
a side-effect, rather than a cause.  According to Mr. Bentley, a
carbon-fouled plug could be caused by too much fuel.

> Check all your vacuum lines, and try unplugging the OXY sensor.  Let me
> know what unplugging it results in and what you find on the dwell meter
> hooked to the test port on the Jetronic harness (proceedure is in the
> Bentley)

I'll try to do that tomorrow.

> What did you find with the Coldstart valve?  Is it leaking?

I didn't see any signs of leaking...

Thanks again for all your help!

Mike Carlson
'84 Scirocco Wolfsburg Edition (slightly ill)
'95 GTI VR6
http://www.divergent.org/mikes.vws/