Help CIS-E III expert !! audi 100 88/NF engine gives persistent 2121 and bad idle

My car has gone crazy, and keeps being smarter than me, unwilling to
get fixed. Now engine behaves like dr. Jackal and Hyde.
Problems:
1) COLDMODE: When started cold, car start fine, runs warm on 800-1000.
When it gets warm, idle gradually drops to 200-300, engine nearly
stalls, but mostly catches just in time with flashing dashlights. When
driving, it takes gas badly, and hesitates before engine picks up.
Engine sounds very hollow when idling, also slight loss of power seems
to be present.
2) WARMMODE: When car is started warm, it behaves different. Idle is
oscilating fast between 1000-1200. For the rest it runs fine, and takes
gas very well. Also no loss of power seems to be present.
3) Generally, car runs very rich. I replaced OXS-sensor, but still it
smells on gas, specially when running in COLDMODE. Turning down CO
screw only results in unability to restart at all.

Because i don't like breaking with left foot to keep engine alive when
car has to stop, i removed ISV connector. Without ISV connector, car
shows constant WARMMODE behaviour.

In the last month i changed and cleaned all parts involved in air
intake and fuel injection. Fault code 2121 is present, but new idle
switch didn't make the problems and fault code go away.
Changed parts:
1) Seals of intake pipes.
2) Temp. sensor (black).
3) idle switch.
4) Injector inserts, and o-rings.
5) Plugs/air filter/oil.
6) OXS sensor.
7) Valve conver seal.
8) Fuel pump is 1 yr. old.
9) Changed cold start Valve, original is suspected to leak or not close
properly.

Question:
I am now at the level where i am desperate. What should i do next ?.
All help is very much appreciated.

that code seems to point to throttle switch.
http://www.12v.org/maintenance/dtc.php?code=2121

"2121
Closed Throttle Position Switch. Possible Cause Corrective Steps
a.. Closed Throttle Position (CTP) switch needs adjustment
a.. Throttle valve sticking
a.. Floor mat presses on accelerator pedal
a.. Accelerator pedal cable needs adjustment
a.. Open circuit in wiring to connector A, terminal 9 of ECM
a.. Input for CTP in ECM faulty (ECM is faulty)
a.. Connector A, terminal 9 of ECM has short circuit to ground
a.. Moisture in throttle connector
a.. Check CTP output
a.. Adjust accelerator pedal cable
a.. Repair open/short circuit in wiring

Error is stored if the throttle opening is greater than 7° and the CTP
switch is closed for longer than 1 second, or if the CTP switch has not been
closed at least once as soon as the engine has been started and there has
been a 10 minute drive under 62mph. "

Usually I find that the wires going to the switch break before the plug.
Or the throttle is not fully closing. Does your 100 have a secondary
throttle plate? Possibly it is stiff and does not fully close.

Do you have the Bentley repair manual? If so you can do a multimeter test
from the ECM plug and check out the FI system/sensors/switches.

good luck,
dave



> wrote in message
oups.com...
> My car has gone crazy, and keeps being smarter than me, unwilling to
> get fixed. Now engine behaves like dr. Jackal and Hyde.
> Problems:
> 1) COLDMODE: When started cold, car start fine, runs warm on 800-1000.
> When it gets warm, idle gradually drops to 200-300, engine nearly
> stalls, but mostly catches just in time with flashing dashlights. When
> driving, it takes gas badly, and hesitates before engine picks up.
> Engine sounds very hollow when idling, also slight loss of power seems
> to be present.
> 2) WARMMODE: When car is started warm, it behaves different. Idle is
> oscilating fast between 1000-1200. For the rest it runs fine, and takes
> gas very well. Also no loss of power seems to be present.
> 3) Generally, car runs very rich. I replaced OXS-sensor, but still it
> smells on gas, specially when running in COLDMODE. Turning down CO
> screw only results in unability to restart at all.
>
> Because i don't like breaking with left foot to keep engine alive when
> car has to stop, i removed ISV connector. Without ISV connector, car
> shows constant WARMMODE behaviour.
>
> In the last month i changed and cleaned all parts involved in air
> intake and fuel injection. Fault code 2121 is present, but new idle
> switch didn't make the problems and fault code go away.
> Changed parts:
> 1) Seals of intake pipes.
> 2) Temp. sensor (black).
> 3) idle switch.
> 4) Injector inserts, and o-rings.
> 5) Plugs/air filter/oil.
> 6) OXS sensor.
> 7) Valve conver seal.
> 8) Fuel pump is 1 yr. old.
> 9) Changed cold start Valve, original is suspected to leak or not close
> properly.
>
> Question:
> I am now at the level where i am desperate. What should i do next ?.
> All help is very much appreciated.
>

Hi dave,

> Usually I find that the wires going to the switch break before the plug.
> Or the throttle is not fully closing. Does your 100 have a secondary
> throttle plate? Possibly it is stiff and does not fully close.
You ask if throttle does not close well and let pass air into engine
although it should be closed ?.

I checked throttle body. connected multimeter to terminals 1-2 of
connector, and as soon the throttle is moved little, switch opens. Same
holds for full-throttle switch. On the plug ends there is 12V.

>
> Do you have the Bentley repair manual? If so you can do a multimeter test
> from the ECM plug and check out the FI system/sensors/switches.
>
I have Bentley manual, and tested cables from ecm plug to terminal,
will check again if there is a ground-leak or short.

You have a clue why engine is running in two modes when ISV is
connected ?. Sometimes it looks as if ISV tries to regulate engine
speeds, but can not hold it because something is out of spec.


> good luck,
> dave
Thx very much again.
>
>

REPLIES WITHIN

> wrote in message
ups.com...
> Hi dave,
>
>> Usually I find that the wires going to the switch break before the plug.
>> Or the throttle is not fully closing. Does your 100 have a secondary
>> throttle plate? Possibly it is stiff and does not fully close.
> You ask if throttle does not close well and let pass air into engine
> although it should be closed ?.
>
> I checked throttle body. connected multimeter to terminals 1-2 of
> connector, and as soon the throttle is moved little, switch opens. Same
> holds for full-throttle switch. On the plug ends there is 12V.

But if there is a secondary butterfly valve, that 2nd valve could be staying
open just a hair creating a problem like you are describing.
Sounds like things are good there electrically.

>
>>
>> Do you have the Bentley repair manual? If so you can do a multimeter
>> test
>> from the ECM plug and check out the FI system/sensors/switches.
>>
> I have Bentley manual, and tested cables from ecm plug to terminal,
> will check again if there is a ground-leak or short.
>
> You have a clue why engine is running in two modes when ISV is
> connected ?. Sometimes it looks as if ISV tries to regulate engine
> speeds, but can not hold it because something is out of spec.

That is why checking from the ECM plug is a good way to find/test out the
system electrically.
Don't forget that mechanical things can create problems like the throttle
body plates, fuel distributor and boot, etc.
Does EVERYTHING check out within specs? How is the coolant temperature
sensor?
How is the fuel pressure? Too much, too little or just right?

That code is pointing you to the throttle body though!!
What year is this Audi?

thinking out loud!
--
later,
dave
(One out of many daves)

One out of many daves schreef:

> REPLIES WITHIN

> >> Usually I find that the wires going to the switch break before the plug.
> >> Or the throttle is not fully closing. Does your 100 have a secondary
> >> throttle plate? Possibly it is stiff and does not fully close.
> > You ask if throttle does not close well and let pass air into engine
> > although it should be closed ?.
> >
> > I checked throttle body. connected multimeter to terminals 1-2 of
> > connector, and as soon the throttle is moved little, switch opens. Same
> > holds for full-throttle switch. On the plug ends there is 12V.
>
> But if there is a secondary butterfly valve, that 2nd valve could be staying
> open just a hair creating a problem like you are describing.
> Sounds like things are good there electrically.
Throttle body has two plates inside, a big one, and a much smaller one.

To be sure i wil replace it, have another one around.
If the plates do not close, then the body is worn out ??, i do not see
what can be done about a throttle that does not close well.
I replaced original body with one from a NG engine, it looks
equivalent, inside it was very nicely polished, and seemed to work
fine. On this NG body new idle and full-throttle switches were
assembled. I see you point, the original NF body has an extra thicker
plate on the small plate, which gives larger closing surface with
inside of throttle body. Because the NG body does not have this, air
might be passing through the small plate, causing vacuum problems.


> >
> > You have a clue why engine is running in two modes when ISV is
> > connected ?. Sometimes it looks as if ISV tries to regulate engine
> > speeds, but can not hold it because something is out of spec.
>
> That is why checking from the ECM plug is a good way to find/test out the
> system electrically.
> Don't forget that mechanical things can create problems like the throttle
> body plates, fuel distributor and boot, etc.
> Does EVERYTHING check out within specs? How is the coolant temperature
> sensor?
> How is the fuel pressure? Too much, too little or just right?
Coolant sensor is brand new from audi dealer, haven't checked if it is
good. will do.
Fuel pressure should be good, first the pump is an original Pierburg
less then a year old, second, and that is actually the frustrating
part... Car drives like a dream when it is not in idle, takes gas good,
and seems to have sufficient power.
Since car is not holding back when full throttle is applied at higher
speeds, fuel quantity and pressure should be in spec ??, i have no
tools for measuring the fuel pressure.
Connectors on potentiometer en fuel pressure regulater check ok.


> Don't forget that mechanical things can create problems like the throttle
> body plates, fuel distributor and boot, etc.
I know, the problems started two months ago, car stopped because it
suddenly ran extremely rich, and chocked all plugs in tar. The whole
intake system looked as if car was run on coles. Since then i cleaned
everything, and replaced all seals, cleaned fuel distributor and
checked air distibutor. Everything seemed to be ok, if plunger plate is
lifted with fuel pressure, it goes evenly, but heavy.
Can fuel distributor be worn out ???

>
> That code is pointing you to the throttle body though!!
> What year is this Audi?
It is a 1988 NF 2.3E, with facelift (new doorhandles). Idle was never
as stable as with my simple K-Jetronic 5cylinder quantum (passat) from
1985.
>
> thinking out loud!
I apreciate your thinking very much, it helps me to get closer to this
ghost that is spoiling the pleasure on this great car.
So far, actionplan is as follows:
1) Check wires from ecm
2) Replace throttle body, recheck idle switch position
3) Check temp. sensor


> --
> later,
> dave
> (One out of many daves)
You'r the best !.

Erik

REPLIES WITHIN and edited

>> > I checked throttle body. connected multimeter to terminals 1-2 of
>> > connector, and as soon the throttle is moved little, switch opens. Same
>> > holds for full-throttle switch. On the plug ends there is 12V.

WAIT are you saying the full-throttle switch activates as soon as you open
the throttle?
Shouldn't it activate only at WOT (WIDE OPEN THROTTLE)?
Have to check this! ;-)

>>
>> But if there is a secondary butterfly valve, that 2nd valve could be
>> staying
>> open just a hair creating a problem like you are describing.
>> Sounds like things are good there electrically.
> Throttle body has two plates inside, a big one, and a much smaller one.
>
> To be sure i wil replace it, have another one around.
> If the plates do not close, then the body is worn out ??, i do not see
> what can be done about a throttle that does not close well.
> I replaced original body with one from a NG engine, it looks
> equivalent, inside it was very nicely polished, and seemed to work
> fine. On this NG body new idle and full-throttle switches were
> assembled. I see you point, the original NF body has an extra thicker
> plate on the small plate, which gives larger closing surface with
> inside of throttle body. Because the NG body does not have this, air
> might be passing through the small plate, causing vacuum problems.

Corrosion usually causes the throttle plates to slightly stick open here in
Chicago. I can usually get them to work properly with some penetrant and
elbow grease.

>
>
>> >
>> > You have a clue why engine is running in two modes when ISV is
>> > connected ?. Sometimes it looks as if ISV tries to regulate engine
>> > speeds, but can not hold it because something is out of spec.

I have not worked on many of your engines so I am not sure if it has a cam
sensor or even a crank sensor (Engine Speed Sensor). I would venture to say
NO it is not present. Correct me if I am mistaken.

>>
>> That is why checking from the ECM plug is a good way to find/test out the
>> system electrically.
>> Don't forget that mechanical things can create problems like the throttle
>> body plates, fuel distributor and boot, etc.
>> Does EVERYTHING check out within specs? How is the coolant temperature
>> sensor?
>> How is the fuel pressure? Too much, too little or just right?
> Coolant sensor is brand new from audi dealer, haven't checked if it is
> good. will do.
> Fuel pressure should be good, first the pump is an original Pierburg
> less then a year old, second, and that is actually the frustrating
> part... Car drives like a dream when it is not in idle, takes gas good,
> and seems to have sufficient power.
> Since car is not holding back when full throttle is applied at higher
> speeds, fuel quantity and pressure should be in spec ??, i have no
> tools for measuring the fuel pressure.
> Connectors on potentiometer en fuel pressure regulater check ok.

That FPR is electronically controlled and you can monitor current flow with
a Digital Volt Ohm Meter AFAIK.
I have seen some vehicles run with a bad FPR and some not.
Need current to that FPR and I have seen some people mistakenly remove the
fuse! 8^o

>
>
>> Don't forget that mechanical things can create problems like the throttle
>> body plates, fuel distributor and boot, etc.
> I know, the problems started two months ago, car stopped because it
> suddenly ran extremely rich, and chocked all plugs in tar. The whole
> intake system looked as if car was run on coles. Since then i cleaned
> everything, and replaced all seals, cleaned fuel distributor and
> checked air distibutor. Everything seemed to be ok, if plunger plate is
> lifted with fuel pressure, it goes evenly, but heavy.
> Can fuel distributor be worn out ???
>

If the fuel pressure is too high won't that cause more fuel to come out of
the injectors?
Possibly fuel distributor, but I would not change that yet.
Wires to the Oxygen Sensor shorting out can cause a rich mixture


> So far, actionplan is as follows:
> 1) Check wires from ecm
> 2) Replace throttle body, recheck idle switch position
> 3) Check temp. sensor

I would check and not replace the TB! ;-)
--
later,
dave
(One out of many daves)