91 100 Rough idle and no throttle response after warmup - Update

[SJ]

Update on the 91 100  problem:
- disconnected "choke" injector after starting up car . . . .ran fine . .
.means there are no major vacuum leaks.
- problem must be with fuel system

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.

0min 0sec - Started car, outside temp was about 50 F
Reg current at 100ma, oxy sens reads -1.0v

0min 30 sec - reg current at 30ma, ox sens -.5v

4min 0sec - reg current steadily dropped to 5ma over the 3 1/2 minutes, ox
sens at -.5v
disconnected choke injector . . engine idles ok.

4min 30sec - reg current at 3ma, ox sens at -.5v
5min 00sec - reg current at 3ma, ox sens at -.5v
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
9min 00sec - reg current goes negative, ox sens goes to +1.8v
                   - engine RPM drop rapidly, engine stalls
10min 00sec - disconnect ox sens - start engine - idles ok - reg current at
0ma

Ground ox sens terminal at harness connector -  rich stop mode
reg current climbs slowly to 15 ma over 12 seconds . . . engine runs fine

Remove ground - open loop mode
reg current drops rapidly to 0ma . . .engine runs fine

Connect 1.5v battery + to ox sens harness connector - lean stop mode
reg current drops slowly to negative 15ma over 15 seconds . . . .engine
stalls.

Now I have to figure out what all this means. I think the oxygen sensor is
bad.

When the engine warms up and the engine temp sensor tells the computer to go
into closed loop mode, the computer gets the bad signal from oxygen sensor
and leans out the mixture and engine dies.

Put the car up on ramps and had a look at the oxygen sensor. Sensor looks
like the original one. No way in hell you can take it out without dropping
the catalytic converter. The auto tranny blocks access for tools. The cat
bolts are rusted out . . they look like 1/10 the original diameter. The
oxygen sensor wiring is still in the original clips. Car has 109,000 miles
on. Sure looks like original sensor.

Went to start up my 88 5kq  . .wanted to see what the ox sensor voltage
readings are as the engine warms up.
The engine starts, then dies . . .what the @%&#$&*@# !!!!
Starts ok, then dies. Geez, maybe the car is having sympathy pains? Will my
problems never end?!!

Can someone verify that my analysis is correct?

Syl
88 5kq
90 100q
the patient > 91 100










----- Original Message -----
From: "SJ" <syljay at optonline.net>
To: <quattro at audifans.com>
Sent: Sunday, October 13, 2002 10:33 AM
Subject: 91 100 Rough idle and no throttle response after warmup


> I'm working on a friends car . . .putting in new heater blower motor . . .
.
> what a PTA job!!!
>
> He bought this car about a month ago . . .no history on previous owner or
> service done.
>
> Patient is 91 100, non turbo, non quattro, auto trans, 5 cyl engine.
>
> Car ran fine when I drove it to my house for the repairs. Now after a
couple
> of days; I started it up and it ran fine . . idle works, throttle works.
> After a few minutes warm up, it starts running a bit rough and there is no
> throttle response. Operating the throttle valve by hand produces no RPM
> increase. Its as if the throttle valve was disconnected.
>
> Sounds like a stuck air flow sensor in the fuel distributor? I'll have a
> looksee at that later today and clean it out. Might as well clean out the
> ISV valve while I'm at it. And take a look at the air filter . . .I bet
that
> was'nt changed for a long time. Mechanics find it too hard to get at.
>
> Any other BTDT's on this problem?
>
> Thanks
> Syl
> 88 5kq
> 90 100q
>
>
>