Re: CIS-E mixture Q's

[Brett Van Sprewenburg <brett@netacc.net>]

>Hey all,
>
>Just a couple questions here for the CIS-E gurus ...
>
>I hooked up an ammeter inline with the DPR on my 16v a couple days ago and
>got a reading of 9.92 mA. It wasn't really fluctuating.. it went
>up to 9.93 mA occasionally.

This strongly indicates that something is not working properly, given that
you hooked up the meter correctly, and it was in working order (sounds
like you had that well in hand though).

>I hooked a voltmeter to the oxygen sensor
>(with the sensor disconnected) and the voltage varied from 300 mV to 650
>mV, very irregularly. Always jumping around, with no apparent
>pattern. The O2 sensor is 6 months old.

I am not familiar with what a working O2 sensor puts out as a voltage,
but this seems to be reasonable.  Perhaps you have a poor / broken
harness connection in the feedback circuit?

>This is telling me two different
>things - the O2 sensor is saying that I'm running rich and the DPR is
>saying that I'm running lean.

I don't know what the O2 mV -> mixture relationship is, so I can't
comment on your conclusions.

>That's based on the idea that the
>oxygen sensor produces a voltage proportional to the amount of oxygen in
>the exhaust gases where stoich = ~700 mV, and that a lower DPR current
>signifies a richer mixture.

I'll take your word on that. :)  However, I _believe_ (and could very
well be incorrect) that the lower DPR current actually signifies less
correction to the injector fuel pressure, by applying less control
pressure to the flow diaphragm , which in turn, as you say, usually
results in a richer mixture assuming equal fuel pressure.  Just one
of the reasons why a 1K ohm resister in place of the CTS doesn't always
result in the same DPR reading on different cars, and same 'enrichment'.
Which in turn is why any CIS-E fuel enrichment device must be adjustable
to car it's on, but I digress. :)  See at all what I am trying to say?

>
>If I remember correctly the DPR is supposed to be 4-6 mA averaging 5
>mA. "Continuously fluctuating". What's going on? Anybody have any insight
>as to why the DPR current is basically constant? The oxygen sensor is
>plugged in and everything.

The circuit isn't functioning properly, the usual culprit is a non-functioning
O2 sensor, or an apparent non-functioning O2 sensor through poor connections.

>
>Also, someone may have tampered with the mixture in the past, or at least
>tried to. My mixture plug is basically completely drilled out .. or the
>soft metal top, at least. I don't think theres any chance of getting it
>out with a sheet metal screw. Any suggestions for how to get it out?

Can you see down into the dist through that tiny hole?  Try putting in
a 3mm hex wrench, and feel around for the set screw, you'll know when
you hit it.  I have a feeling it's probably drilled out fully.

>
>
>Any suggestions would be appreciated..

Just the thoughts above, which probably don't help you very much.  Learned
anything new in the mean time?  When Jim Jarrett went though something
similar, he ended up going through something like 3 O2 sensors and an
O2 'brain-box' before coming up with a combo that worked as advertised.

>
>Thanks,
>
>-Toby


==Brett

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | - brett@netacc.net

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