Yvan

Anyone knows location of ISV Control Unit on 5-cyl. 1989 Audi 100?

It is not in the aux relay panel (by drivers left knee under dash) as can be seen on photos:

http://photos.yahoo.com/perlica

tonyj

A few of us on the newsgroup have been trying to help him with several things on his DUAL FUEL Gas / LPNG '89.

Yvan is in Eastern Europe so that is why he mentions the '89 100.

I had described the double wide relay in the aux panel but he woesn't seem to have one.

I thought I remember that some years the ISV is controlled by the ECU ???

itsav8

The controll unit is in the driver side kick pannel. Under were the hood release is.
Ron

auditech1218

The idle stabilizer function is integrated in the fuel injection ecu in the passenger kick panel however the ignition control unit in the driverside kick panel can also influence its operation in 89 and up audi 100 opposed to being completly controlled by the fuel injection ecu in pre 89 (Audi 5000) which also had engine code NF

tonyj

that he has been experiencing very high idle and has been doing a lot of research and work to figure it out.

Apparently he starts on gas and then switches over to LP once it is running.

Steve Sears, on the ng (very knowledgeable) has been thinking that the location where he is injecting the LP (IM I think, would cause the ISV to operate just opposite of what it is suposed to do because the volume of LP added at that point would throw off the air fuel mix into an undefined state.

-------------- Steve's thoughts
Yvan,
The temperature:rpm correlation should be about right, as the LPG will turn to a more diffuse gas with greater heating, and you are using the engine coolant to heat the LPG, right?
It sounds like the ISV is indeed working, but the feedback from it being designed for a different purpose than LPG sounds like it may be causing the problem (by working properly!) - I suggest that you may have to rig in a way to disable the ISV when you are running LPG, as the engine runs properly when you're running on gasoline, correct? Thus, when the LPG turns on (engine at required temperature), then you would have to take the ground connection away from the ISV. I expect that there may be a relay doing that already - to shut off the fuel pump.
---------------------------

I really didn't follow the logic on that but it sounded possible.

Will Ng

<center><img src="http://pictureposter.audiworld.com/38606/200q_door_harness_2.jpg"></center><p>Only the 200s have the ISV controller by the left side kick panel. It's the black item at the bottom of the picture.

The ignition control unit resides there for a 100.
And fuel control unit is under right side kick panel.

Yvan

No, I do not have high idle problem. My problem is that engine will sometimes stall when the vehicle pulls up at traffic lights etc. When I stop, rpm goes down to ~550, sometimes stall, or go up to ~900, and then settle at usual idle at ~700.

Rpm going down below usual idle is noticeable on gas too, but less than when it is on on LPG.

LPG is mixed with air in mixer located inbetween "michelin" hose and intake manifold. I have open loop system (O2 sensor is not used).

Will Ng

It collects the fuel tank vapors. When the engine is running, the vapors are sucked out to the air boot before the throttle plate. This is regulated by a frequency valve and the cycle is based on engine speed and load. If this valve is defective it may be a source of vacuum leak or throw your air/fuel ratio off.

Looking at a picture of the 100 intake, shows the fuel injectors have the air shroud feature which has the air supply provided by the same hose as the ISV. This hose claims to be connected to the intake air boot. Since you are introducing the fuel mix in the air boot (before the TB), any leaking o-rings around the injectors will provide propane and air to bypass the throttle body.
IMO I don't think the ISV is at fault if the mix is correct. If it operates, you should only experience a higher idle, right?
The engine should hold steady idle w/o the ISV. Pinch off the supply hose to verify the ISV is not the cause of the low idle. Then pinch off the air shroud hose to check the for o-ring leakage.
(Personally, I was never too sure as to the purpose of air shrouded injectors.)

Yvan

I have carbon cannister. And I think that frequency valve is working OK (there is ticking sound on idle).

English is not my native language, so I have a little trouble understanding your post. What is "air shroud feature"? On LPG mixer located just before the TB (and after "michelin" hose) is a connector where is connected hose that used to be connected in the middle of "michelin" hose, and that goes in one plastic thing (again my bad English) from where one (~1" thick) hose goes to ISV, and another (~1/5" thick) short hose goes into intake manifold. Is that short hose what you are referring as "air shroud feature"? I will post some photos if you want.

What do you mean by stating that if ISV works I "should only experience a higher idle"? Why should idle be higher? If it works idle should be normal (700 rpm in my case).

I disconnected electrical connections to ISV, and engine idles fine when warm (&gt;60 deg. Celsius). If it is colder, idle is low, less than normal, and it will stall. If it is hotter (say normal operating temperature) it will idle steady bot on higher (~800-~900 rpm). If i blip the throttle it will go down to normal ~700 and stay there.

With ISV disconnected (electrical connection) I do not experience stalling, or near stalling problem.

Few months ago I sprayed every injector with carburetor cleaner and noticed no change in idle rpm.

I also noticed another thing that seems not right. When I disconnect connector to idle and full throttle switch ISV is still working (correcting idle). As I understood what I read on Audi NG, ISV is ON when idle switch is ON. Correct?

Will Ng

1. carbon cannister:
OK, we'll assume that system is working normally.

2. I think your English is excellent. I will try to explain more clearly. The "air shroud" is what Audi calls this system. It's function is not described well in the Bentley(US) offical factory repair manual. Basically, the mechanical fuel injectors sit within a cavity in the intake manifold. These cavities are connected to an air source before the throttle body. It's function is unclear to me.
The 1/5" inch thick hose you discovered is for the 'air shroud'.

3. The ISV only increases the idle rpm from the preset static idle rpm. the air bleed screw at the throttle body should be closed and idle should be 700 rpm w/o ISV function. The ISV when functioning should maintain idle at ~750 rpm for an NF (and 800 rpm for a MC). It is also used to compensate for heavy electical load. Duty cycle increases for ~200 rpm increase when AC/system ON and HI.
The ISV duty cycle is designed for gasoline and closed loop. Since you are introducing (gaseous?) propane before the throttle body, if the ISV functions, air and fuel is bypassing the throttle body, not just air alone. How are you regulating the propane mixture? vacuum? I wonder if the ISV duty cycle may be causing excess lean conditions.

4. With the ISV disconnected, you should always get ~700 rpm for idle. With a cold engine, mixture must be richer for smooth idle, and the 800-900 rpm when hot, makes me suspect you are running too lean. The fact that blipping the throttle causes the idle to return to 700 rpm may indicate the propane regulation is not precise enough.

5. As I mentioned in #2, I think the ISV function is interfering with your method of propane open loop regulation.

6. spraying around externally only proves there are no external vacuum leaks around the large o-rings of the injectors.
Have you also checked the crankcase ventilation hoses for leaks?

7. According to the Bentley manual, each switch has 3 pins: 1/2/3. Pin 2 is +12V supply.

full throttle switch: should be infinite ohms between pins 2 and 3 when open. 0 ohms when closed at full throttle.

idle switch: should be 0 ohms between pins 1 and 2. And with 0.5 mm movement to throttle, resistance becomes infinite.

Therefore, the ISV should not function when you disconnect both switches. Something is wrong. Bentley states to check the idle switch function first. If OK, test full throttle switch, if OK, check wiring harness to fuel control module. If wiring is OK, you have a faulty module.

ISV only functions during idle, inactive during partial throttle, and momentarily at full throttle (according to diagnostic).

Hope that helps. Sorry I'm not an expert on NF's.
Your propane project is very cool!