91 100 Rough idle and no throttle response after warmup - Solved!

[Ray Rollins]

SJ,
Have you pulled the radio out of the dash to see if the code is written on
it? Most of these units didn't last more than 2 years before failing and
alot of the replacements have the code written on the case. If I were in
your position and I could not find the code,I would replace the orignal unit
with an Alpine.

Good Luck,
Ray
90 100Q

>From: SJ <syljay at optonline.net>
>To: quattro at audifans.com
>Subject: 91 100  Rough idle and no throttle response after warmup - Solved!
>Date: Mon, 21 Oct 2002 13:25:44 -0400
>
>
>Huw wins the fair maiden for his correct diagnosis - -> defective Oxygen
>sensor.
>
>The problem was the oxygen sensor. I had to drop the catalytic converter to
>get at the oxygen sensor. Of course, the cat hardware was replaced with
>Stainless Steel, ala Huw.
>
>There was a dramatic difference in performance after installing the new
>oxygen sensor. Car had lots more Ooooomph! The old sensor looked pretty
>ratty. I think it was the original sensor(100K plus miles).
>
>With the new oxygen sensor , the sensor voltages and fuel regulator current
>readings are:
>
>Ignition on    -  reg current at 100ma, O2 voltage at .5v (This voltage is
>provided by the ECU)
>Start            -   reg current at 70ma, O2 at .6v
>Warmup       -  reg current steadily drops to 3ma , O2 voltage stays steady
>at about .7v - then starts swinging between .2v and .9v as system goes into
>closed loop mode. Time to closed loop was about 3 minutes.
>
>I found an article at       http://www.mr2.com/TEXT/O2_Sensor.html
>which
>explains how to test the sensor on the bench. I tried the technique and it
>worked. I tested the new sensor before installing it.
>
>I paraphrase the article below:
>
>1. Clamp O2 sensor in vice, attach digital DC voltmeter to sensor. Gnd to
>sensor body, Pos to black sensor lead.
>2. Propane torch set to high, heat perforated sensor tip - - should see at
>least .6V within 20 seconds.
>3. Remove heat - - voltage should drop to under .1V within 4 seconds.
>4. Heat for 2 minutes and watch for drops in voltage.
>5. Move the flame back and forth over the sensor - voltage will quickly
>change from high to low.
>
>Test Summary: Any sensor that generates 0.9 V or more when heated, show
>0.1V
>or less within one second of flame removal, and pass the 2 minute heat test
>is good regardless of age.
>
>Now I need to figure out how to reset the radio code . . .its on "SAFE".
>Fix one thing and find two more things to fix. I doubt the car owner has
>the
>code for it. Looks like a trip to the dealer so that they can pull the
>radio
>and look up the radio serial number on the computer to get the code. How
>much do they charge for that?
>
>SJ
>88 5kq
>90 100q
>
>=3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =
=3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D=
 =3D
>=2E
> > I hooked up an ammeter to measure Differential Pressure Regulator
>Current.
> > And I hooked up a digital voltmeter to the oxygen sensor lead, oxy
>sensor
> > connected to harness connector.
>
> > 5min 30 sec - reg current at 15ma, ox sens at -.5v
> > 6min 30sec - reg current at 20ma,ox sens at -.5v
> > 7min 00sec - reg current at 18ma,ox sens at -.5v
> > 7min 30sec - reg current at 3ma,ox sens at -.5v
>
> > Now I have to figure out what all this means. I think the oxygen sensor
>is
> > bad.
>
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>- - - - - - - - - - - - -
>
>Me too.  The OXS voltage is supposed to fluctuate steadily over a few
>second cycle, up and down around .5 volts.  Yours appears to be locked
>into .5 v, which is probably due to the presence in the ECU of a "ghost"
>voltage produced by the circuitry therein (you should be able to measure
>this .5 v at the OXS harness, ECU side, with the OXS unplugged).
>
>with it unplugged you should run ok, in the fairly decent limp home mode
>of CISE3 (defaults to 0 mA).
>
>with it working, the DPR current should flustuate as the OXS voltage
>does, above and below 0 mA, btw.
>
>--
>Huw Powell
>
>http://www.humanspeakers.com/


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