Driving with disconnected ISV?

I have hmmm... dual fueled 1989 Audi 100 2.3E (NF 5-Cyl. engine). I
start engine on unleaded petrol, and after few minutes ('till engine
warms up) it switches to LPG (see http://www.lpga.co.uk/LPGA.htm). It is
LPG system of an older generation without lambda (O2) gas control.

When I stop the car rpm drops to some 500-600 and then sometimes stalls,
and sometimes goes up to 900-1000 and then back to standard 750.

I was wondering if I can disconnect ISV or switch that goes on when
throttle pedal is released (I can not remember it's name, English is not
my native language), switch that activates ISV. Does that switch do
something else? Could i do any damage by disabling it? Or by
disconnecting ISV?

On LPG system I can adjust idle by turning a knob, but it seems that ISV
is slow in reaction when throttle pedal is released, so to confirm that
I want to try driving with ISV disconnected, but I am afraid of possible
damage to other systems.

--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
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Yvan,
I must admit I have no knowledge of the LPG system or how it runs. With a
normal engine, the throttle switch tells the idle stabilization system when
the throttle is at idle, and the ISV should regulate rpm. It sounds like
you have a sticky ISV - which you should clean with _throttlebody cleaner_
(NOT CARBURETOR CLEANER), or check the condition of the throttle switch. If
the ISV is a 2 contact unit, if you can blow through the unit (after it's
cleaned, of course) without power, then it's no good. If it's a 3 contact
unit, then it is supposed to allow air through at rest. When you clean the
ISV, use a 9volt battery to make the valve click to ensure that it is not
siezed. If the LPG system acts like a normal fuel system, the shutdown of
the switch or of the ISV shouldn't harm it, it will just idle poorly.
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

"Yvan" > wrote in message
...
> I have hmmm... dual fueled 1989 Audi 100 2.3E (NF 5-Cyl. engine). I
> start engine on unleaded petrol, and after few minutes ('till engine
> warms up) it switches to LPG (see http://www.lpga.co.uk/LPGA.htm). It is
> LPG system of an older generation without lambda (O2) gas control.
>
> When I stop the car rpm drops to some 500-600 and then sometimes stalls,
> and sometimes goes up to 900-1000 and then back to standard 750.
>
> I was wondering if I can disconnect ISV or switch that goes on when
> throttle pedal is released (I can not remember it's name, English is not
> my native language), switch that activates ISV. Does that switch do
> something else? Could i do any damage by disabling it? Or by
> disconnecting ISV?
>
> On LPG system I can adjust idle by turning a knob, but it seems that ISV
> is slow in reaction when throttle pedal is released, so to confirm that
> I want to try driving with ISV disconnected, but I am afraid of possible
> damage to other systems.
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** http://counter.li.org/ **
> /__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Nedavno Steve Sears pise:

| It sounds like you have a sticky ISV - which you should clean with
| _throttlebody cleaner_(NOT CARBURETOR CLEANER), or check the condition
| of the throttle switch.

Throttle switch is OK it goes on just when it is suppose to, and I
cleaned ISV with carburetor cleaner :-( and 9 V battery. Everything
works OK running on petrol, it's LPG that is troubling me.

Hire is in short how it works: Engine is always started on petrol, and
runs on petrol for few minutes, until engine warms up. Then it switches
to LPG. LPG is in liquid state in tank, goes to evaporator (warmed with
coolant from car cooling system so it does not freeze), and there it
evaporates and goes into intake mainfold trough rubber hose. When engine
idles LPG is going trough ISV. So all the electronic, O2 sensor... have
no effect when engine is running on LPG. Sort of very simple carburetor.
Only thing that can be adjusted is idle (with a knob on evaporator).
Since ISV is constantly working I have trouble adjusting idle so I try
to disconnect it but engine died. So it seems that my idea about running
engine with ISV disconnected is no good :-)


| If the ISV is a 2 contact unit, if you can
| blow through the unit (after it's cleaned, of course) without power,
| then it's no good.

It's 2 contact unit, I'll try that.

| If it's a 3 contact unit, then it is supposed to
| allow air through at rest. When you clean the ISV, use a 9volt
| battery to make the valve click to ensure that it is not siezed.

Did that while I was cleaning ISV, it is working. I also did the test by
inserting fuse in one of relay's in fuse box for few seconds, and than
by activating full throttle switch, and it's clicking.


| If the LPG system acts like a normal fuel system, the shutdown of the
| switch or of the ISV shouldn't harm it, it will just idle poorly.

As I said it does, so much for my idea.


BTW how do you adjust timing on this car, how do you loosen distributor
when there is bolt at it's base?

I hope you can understand what I am writing, my English is far from
perfect, and I still have to learn all mechanic words :-)


--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** http://counter.li.org/ **
/__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Yvan,
Although I can't vouch for this, I have heard that you cannot adjust timing
by turning the distributor - as I understand it (or misunderstand it), the
crank position sensor (a magnetic sensor which picks up the passing of a
timing pin on the flywheel) tells the engine control unit when the engine is
at top dead center for cylinder 1, and the engine is run accordingly using
the hall sensor in the distributor as a secondary reference.
Somebody...help me out on this one.....
When you say that LPG is going through the ISV - is the LPG hose connected
to the valve itself, or the intake? The ISV in a normal car acts like a
controllable vacuum leak to stabilize the rpm of the car by controlling the
rise and fall of the metering plate - more vacuum in the manifold ~ plate
rises ~ more gas injected ~ rpm increases. The ISV is designed to leak
unmetered (and unexplosive) air into the engine to drop the plate - if you
have the LPG connected to the ISV so it is leaking explosive LPG.....hmmm.
This might explain how disconnecting the ISV will result in the engine
dying - when the power to the ISV is shut off, the ISV is shut off (or
almost off if it is leaking) - so no LPG to the engine. If sounds to me
like the change in function of the ISV (from a vacuum leak to a fuel
injector) might be the problem with the oscillating idle - when it opens up,
it is expecting to let in more air which would normally drop the metering
plate and reduce the idle - but in this case the opening of the ISV results
in more fuel (LPG) into the engine.....is this right?
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

"Yvan" > wrote in message
...
> Nedavno Steve Sears pise:
>
> | It sounds like you have a sticky ISV - which you should clean with
> | _throttlebody cleaner_(NOT CARBURETOR CLEANER), or check the condition
> | of the throttle switch.
>
> Throttle switch is OK it goes on just when it is suppose to, and I
> cleaned ISV with carburetor cleaner :-( and 9 V battery. Everything
> works OK running on petrol, it's LPG that is troubling me.
>
> Hire is in short how it works: Engine is always started on petrol, and
> runs on petrol for few minutes, until engine warms up. Then it switches
> to LPG. LPG is in liquid state in tank, goes to evaporator (warmed with
> coolant from car cooling system so it does not freeze), and there it
> evaporates and goes into intake mainfold trough rubber hose. When engine
> idles LPG is going trough ISV. So all the electronic, O2 sensor... have
> no effect when engine is running on LPG. Sort of very simple carburetor.
> Only thing that can be adjusted is idle (with a knob on evaporator).
> Since ISV is constantly working I have trouble adjusting idle so I try
> to disconnect it but engine died. So it seems that my idea about running
> engine with ISV disconnected is no good :-)
>
>
> | If the ISV is a 2 contact unit, if you can
> | blow through the unit (after it's cleaned, of course) without power,
> | then it's no good.
>
> It's 2 contact unit, I'll try that.
>
> | If it's a 3 contact unit, then it is supposed to
> | allow air through at rest. When you clean the ISV, use a 9volt
> | battery to make the valve click to ensure that it is not siezed.
>
> Did that while I was cleaning ISV, it is working. I also did the test by
> inserting fuse in one of relay's in fuse box for few seconds, and than
> by activating full throttle switch, and it's clicking.
>
>
> | If the LPG system acts like a normal fuel system, the shutdown of the
> | switch or of the ISV shouldn't harm it, it will just idle poorly.
>
> As I said it does, so much for my idea.
>
>
> BTW how do you adjust timing on this car, how do you loosen distributor
> when there is bolt at it's base?
>
> I hope you can understand what I am writing, my English is far from
> perfect, and I still have to learn all mechanic words :-)
>
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** http://counter.li.org/ **
> /__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Nedavno Steve Sears pise:

| Yvan,
| Although I can't vouch for this, I have heard that you cannot adjust
| timing by turning the distributor - as I understand it (or
| misunderstand it), the crank position sensor (a magnetic sensor which
| picks up the passing of a timing pin on the flywheel) tells the engine
| control unit when the engine is at top dead center for cylinder 1, and
| the engine is run accordingly using the hall sensor in the distributor
| as a secondary reference. Somebody...help me out on this one.....

OK, I was just wondering... Thanks.

| When you say that LPG is going through the ISV - is the LPG hose
| connected to the valve itself, or the intake?

LPG hose (actually two of them - one for idle, and one for all but not
idle - sorry for mu bad English again) is connected to air/fuel mixer
located in front of intake. From air/fuel mixer one hose is going to
angled elbow and from there one small hose to intake, and one bigger to
ISV.

| The ISV in a normal car
| acts like a controllable vacuum leak to stabilize the rpm of the car
| by controlling the rise and fall of the metering plate - more vacuum
| in the manifold ~ plate rises ~ more gas injected ~ rpm increases.
| The ISV is designed to leak unmetered (and unexplosive) air into the
| engine to drop the plate - if you have the LPG connected to the ISV so
| it is leaking explosive LPG.....hmmm. This might explain how
| disconnecting the ISV will result in the engine dying - when the power
| to the ISV is shut off, the ISV is shut off (or almost off if it is
| leaking) - so no LPG to the engine. If sounds to me like the change
| in function of the ISV (from a vacuum leak to a fuel injector) might
| be the problem with the oscillating idle - when it opens up, it is
| expecting to let in more air which would normally drop the metering
| plate and reduce the idle - but in this case the opening of the ISV
| results in more fuel (LPG) into the engine.....is this right?

I think that hose that is going to the ISV delivers LPG/air mixture, not
just pure LPG.

I was wrong when posting my original post stating that engine works OK
on unleaded fuel. Today since my engine stalled almost every time I
stopped in on red traffic light, I switched back to gasoline, and engine
then did not die, but it goes to some 650-700 rpm, shakes, then goes to
800-850 rpm and than back to 750 that it should be idling.

So since timing can not be adjusted, and I changed spark plugs, I should
probably change distributer cap, rotating arm in distributer. Can O2
sensor give that symptoms? I tested it and it oscillates 0.35 V (.17 up
an d .17 down) but it takes 1.2 sec (should be .3 sec). I am not willing
to change it, because I think that it has no role when driving on LPG (I
am not sure about that). Also where I live monthly income is low, (I as
a system administrator in a firm with 500 employees make 300$ for a
month) so I am trying to do repairs myself, and Audi part prices are the
same or higher than in US. I could sell this car, but I love it so much
it is good and served me well for 6 years, I just have to fix this idle
thing.



--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** http://counter.li.org/ **
/__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Yvan,
If the ISV is delivering a mixture of LPG and air, that is still more
burnable than the air it is supposed to deliver. The ISV is usually opened
to drop the metering plate to reduce the amount of fuel going into the
engine - but when your ISV opens, it is letting more LPG into the engine.
It sounds backwards to me.
I would change the cap and rotor as a maintenance item, but if the original
oxygen sensor is still in the car I would consider changing it - doubly so
if the convertion to LPG used any silicone sealants to seal the hose
connections (silicone will coat the OXS). If you can get a cheap price on
_any_ 3-wire oxygen sensor, I would get one and splice it into the Audi
harness, or get to know some local Audi owners and borrow one to see if the
change changes anything - get togethers at pubs are helpful - the flow of
beer seems to increase the loaning of tools and selling of spare parts for
less money ;-)
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

> I think that hose that is going to the ISV delivers LPG/air mixture, not
> just pure LPG.
>
> I was wrong when posting my original post stating that engine works OK
> on unleaded fuel. Today since my engine stalled almost every time I
> stopped in on red traffic light, I switched back to gasoline, and engine
> then did not die, but it goes to some 650-700 rpm, shakes, then goes to
> 800-850 rpm and than back to 750 that it should be idling.
>
> So since timing can not be adjusted, and I changed spark plugs, I should
> probably change distributer cap, rotating arm in distributer. Can O2
> sensor give that symptoms? I tested it and it oscillates 0.35 V (.17 up
> an d .17 down) but it takes 1.2 sec (should be .3 sec). I am not willing
> to change it, because I think that it has no role when driving on LPG (I
> am not sure about that). Also where I live monthly income is low, (I as
> a system administrator in a firm with 500 employees make 300$ for a
> month) so I am trying to do repairs myself, and Audi part prices are the
> same or higher than in US. I could sell this car, but I love it so much
> it is good and served me well for 6 years, I just have to fix this idle
> thing.
>
>
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** http://counter.li.org/ **
> /__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Nedavno Steve Sears pise:

| If the ISV is delivering a mixture of LPG and air, that is still more
| burnable than the air it is supposed to deliver.

Yes, but since there is no gasoline it must be LPG-air mixture.

| The ISV is usually
| opened to drop the metering plate to reduce the amount of fuel going
| into the engine - but when your ISV opens, it is letting more LPG into
| the engine. It sounds backwards to me.
| I would change the cap and rotor as a maintenance item, but if the
| original oxygen sensor is still in the car I would consider changing
| it - doubly so if the convertion to LPG used any silicone sealants to
| seal the hose connections (silicone will coat the OXS).

Yes there is some red stuff that looks like silicone sealant where
air/LPG mixer is located. I just wonder if it is necessary. Does O2
sensor have any influence on anything else but amount of injected fuel?
If not I would be changing it for nothing since I drive 99% of time on
LPG. I tried to disconnect it, but it seems to have no effect on idling
whether engine is on LPG or gasoline. But it's definitely not working as
it should I tested it by some instructions provided by Bosch with
oscilloscope.

| If you can
| get a cheap price on_any_ 3-wire oxygen sensor, I would get one and
| splice it into the Audi harness, or get to know some local Audi owners
| and borrow one to see if the change changes anything - get togethers
| at pubs are helpful - the flow of beer seems to increase the loaning
| of tools and selling of spare parts for less money ;-)

Ha, interesting idea :-) If you think that O2 sensor does have effect on
something else than amount of injected fuel I will buy one and replace
it. Maybe it will not better things, it certainly will not do any bad.



--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** http://counter.li.org/ **
/__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Yvan,
Ideally, I believe that the LPG go through the main intake _only_ and not
also through the ISV.....but I'm sure that the people who designed the
system know their stuff. The use of silicone sealant is troublesopme,
though.
Check out:
http://www.sjmautotechnik.com/troubl.../10vo2sen.html
The oxygen sensor feeds back to the engine control unit, which does figure
in to the idle of the car. Part way down Scott mentions that carbon plugged
slots in the OXS will result in fluctuating idle mixture and idle speed.
That _may_ be your culprit.
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

"Yvan" > wrote in message
...
> Nedavno Steve Sears pise:
>
> | If the ISV is delivering a mixture of LPG and air, that is still more
> | burnable than the air it is supposed to deliver.
>
> Yes, but since there is no gasoline it must be LPG-air mixture.
>
> | The ISV is usually
> | opened to drop the metering plate to reduce the amount of fuel going
> | into the engine - but when your ISV opens, it is letting more LPG into
> | the engine. It sounds backwards to me.
> | I would change the cap and rotor as a maintenance item, but if the
> | original oxygen sensor is still in the car I would consider changing
> | it - doubly so if the convertion to LPG used any silicone sealants to
> | seal the hose connections (silicone will coat the OXS).
>
> Yes there is some red stuff that looks like silicone sealant where
> air/LPG mixer is located. I just wonder if it is necessary. Does O2
> sensor have any influence on anything else but amount of injected fuel?
> If not I would be changing it for nothing since I drive 99% of time on
> LPG. I tried to disconnect it, but it seems to have no effect on idling
> whether engine is on LPG or gasoline. But it's definitely not working as
> it should I tested it by some instructions provided by Bosch with
> oscilloscope.
>
> | If you can
> | get a cheap price on_any_ 3-wire oxygen sensor, I would get one and
> | splice it into the Audi harness, or get to know some local Audi owners
> | and borrow one to see if the change changes anything - get togethers
> | at pubs are helpful - the flow of beer seems to increase the loaning
> | of tools and selling of spare parts for less money ;-)
>
> Ha, interesting idea :-) If you think that O2 sensor does have effect on
> something else than amount of injected fuel I will buy one and replace
> it. Maybe it will not better things, it certainly will not do any bad.
>
>
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** http://counter.li.org/ **
> /__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Nedavno Steve Sears pise:

| Ideally, I believe that the LPG go through the main intake _only_ and
| not also through the ISV.....but I'm sure that the people who designed
| the system know their stuff. The use of silicone sealant is
| troublesome, though.
| Check out:
| http://www.sjmautotechnik.com/troubl.../10vo2sen.html
| The oxygen sensor feeds back to the engine control unit, which does
| figure in to the idle of the car. Part way down Scott mentions that
| carbon plugged slots in the OXS will result in fluctuating idle
| mixture and idle speed. That _may_ be your culprit.

Yes, but disconnecting O2 sensor for a while should solve my problem,
and then I could buy new one.

What about deceleration valve? Do I have one? Could stuck decel valve be
my problem?

I borrowed one ISV from a guy that sells used Audi parts. He only had
one like this:

http://www.sjmautotechnik.com/troubl...c/idlesta2.jpg
which is slightly different then one I have. Borrowed one passed blowing
test (as you mentioned it should be closed with no power). Mine did not,
but looking at how it operates I am almost sure that that is the way it
is suppose to be. With ISV in horizontal position there is a 1 mm gap on
the top of a rotating metal thing that can be seen on the "in" side of
ISV. With 9V power rotates up first closing mentioned 1 mm gap and then
opening gap below it. I hope you can understand this :-)

Anyway, fitting other ISV did not do anything, problem is still hire.

Again I was wondering about decel valve. Perhaps if I have one I could
temporarily disable it to see if it is stuck? As I understand it should
be somewhere on air filter box. I will check tomorrow (hire is night
now) but it would help if I would knew what it looks like.


--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** http://counter.li.org/ **
/__/\____/--\__\ ** Reply at: iimperl - at - ml1 - dot - net **

Yvan,
The system in the 1987 Audi 5000 Turbo/200 used a deceleration valve, the
failure of which could result in the engine stalling (it cuts the fuel
delivery off to the engine when the car decelerates, thus reducing fuel
consumption) - but that is for the fuel system, which your LPG system is not
using. There's a Russian web site that has all the parts diagrams - if you
ask the collective at www.audifans.com - I'm sure someone will send you the
link to the site (it's often referred to as the "Family Album").
I think you should give all of the intake hoses a real close check for
cracks or leaks - also in the connections between the LPG system and the
car's original system hoses - the underside of the intake hoses rots out
first due to oil from the crankcase recirculation (and turbo leaks). When
the car is idling, the intake is under a vacuum and may cause an
intermittent leak in a broken hose - changing the fuel/LPG mixture and thus
the idle.
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)