Re: CIS-E mixture Q's

["T. Reed" <treed2@u.washington.edu>]

> >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
> 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 agree..

> 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?

It's possible. I think I'll pull it out and have a look. I used solder,
crimps and heat shrink when I patched the Bosch O2 sensor into the old
harness. Maybe the old harness is bad or broken somewhere, though. That'd
be a good thing to check out.

> >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?

Roughly. I don't get the connection to the fuel enrichment device,
though. That goes through the coolant temperature sensor, which normally
feeds it's info the the F.I. brain.

> 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.

Thats something I'm definately going to check into. I'll test the
connection between the sensor and the harness, and the harness and the
computer.

> >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.

Nope. Reading that over again, I didn't do a very good job of describing
what it looks like. It's definately not fully drilled out. It might even
be JB welded over, I'm not sure.. This is a horrible drawing but it looks
roughly like this from the side.

_______/-|          /\________  <- top flat surface.
          \_.._-._./
         |          |
         |          |
         |   plug   |
         |          |
         |          |
          ==========
          ==========

It looks like somebody just grabbed a 1/8" drill bit and stuck it where
the plug was and held it there drilling for some time, then realized it
wasn't working and gave up. There is a little metal "lip" around the
outside of the "hole" that is either some metal repair epoxy stuff or was
twisted up from the drilling. I don't know. Somebody has obviously at
least tried to remove the plug in the past, though.

> 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.

Hmm. My knock box is not operational, as far as I know, and I'm still
looking for a new one that is known to work. The box suddenly stopped
giving the fuel pump relay ground (and thus running the fuel pump) about
the same time my windshield "seal" (hah!) dumped water all over my
fusebox. I've checked the wiring from the relay to the box and its all
good, so is the +12v at the relay coil, so the only thing left over is the
knockbox. I don't think that has anything to do with my fuel mixture,
though. Just timing...

Thanks for the thoughts,

-Toby

--
'87 16v


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