CIS-E mixture Q's

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

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. 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. 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. 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.

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.

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?

All this was prompted by my brother tuning his 16v GTI and taking me for a
ride. That thing revs from 4000 rpm to 7000 rpm in under a second, in 3rd
gear! It's just crazy... Before he tuned it, it ran pretty much the same
as my car. In the past he'd been using paper clips to measure the current
on the DPR, then it occurred to him that they might have a different
resistance than the copper wire usually there and since it is such a
precise measurement (the dpr current), it would potentially change the
measurement. Well he borrowed my home made harness (made it with junkyard
plugs) and set the mixture again and now it kicks ass. So that must have
been the problem for him. I also helped him build a fuel module over the
weekend and that helped at high revs even more. I wasn't feeling the kick
from mine like I used to so I checked it out and found out the relay was
dead. Swapped in a new one and its running again. I think the relay coil
burned out - it had infinite resistance across the terminals.

Any suggestions would be appreciated..

Thanks,

-Toby

--
'87 16v


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