Intake Manifold Flap / Anti Shudder Valve weird behaviour

maloosheck

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2006 Jetta TDI PD (BRM engine code):

My IMF/ASV is dead. It does not move at all. Bought the brand new one to replace the dead one and here is what is happening:

When I turn on the ignition the IMF closes to approx. 30% and few seconds after starting the engine it fully closes, shutting the engine off.

Is the new IMF faulty?

Or is it possible that the EGR valve is also shot and it does not open when the IMF closes (the engine was cold)?
 
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maloosheck

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Nobody can chime in?

Well, I will be pulling out the EGR valve probably tomorrow to check out if it works or not, maybe it is just stuck closed, but I have no fault code from EGR.
 

mtbr297

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I'd say you have a faulty asv. It is only supposed to close when you turn the key off. Stuck open egr valve won't cause the asv to shut. You may also have some faulty wiring or connectors. Use vagcom and see if it functions properly. How is the 4motion coming along? I about ready to start on my r32 to tdi swap.
 
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maloosheck

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I'd say you have a faulty asv. It is only supposed to close when you turn the key off. Stuck open egr valve won't cause the asv to shut. You may also have some faulty wiring or connectors. Use vagcom and see if it functions properly.
I have no fault codes with the new IMF/ASV, I just cannot run my engine longer than few seconds.

Pulled out the whole piece with the EGR valve and it does not seem to be stuck closed. It opens a bit (I have reduced EGR cycle in my chip tuning), but at the same time the IMF/ASV fully closes.

Can anybody do me a favour, pull out the pipe at IMF and make a short clip starting the COLD engine? There won't be any fault as long as you do not go over idle.

How is the 4motion coming along? I about ready to start on my r32 to tdi swap.
As soon as the '85 MF is out the door up and running, Jetta gets the 4Motion swap.
 

nord

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Very simply... Pull the ASV connecter and see what happens. You'll set a fault but should suffer no driveability issues. Next step is to determine why the ASV is closing. There should be no appreciable current flow until shutdown.

Since I can't remember whether this circuit is voltage actuated or ground actuated I specified "current" flow. Easy enough to test either way as there should be nothing there to activate the ASV motor until you shut down.

A meter across the leads (motor disconnected) and set to voltage will do nicely. If you see nothing out of the ordinary then test ASV for continuity to ground. It should be totally insulated.
 

nord

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For heavens sake, disconnect the thing as I directed! You'll know immediately whether the ASV is your problem and the worst thing that will happen is a code will be set.

After you disconnect and verify, then you can take your good old time and diagnose the root of the problem.

Or sit on your hands and hope for local help. You decide.
 

maloosheck

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For heavens sake, disconnect the thing as I directed! You'll know immediately whether the ASV is your problem and the worst thing that will happen is a code will be set.
I am not sure I properly explained my problem.

My old ASV is dead: the teeth are stripped, the flap does not move, the code is thrown.

The new ASV I ordered is weird: there is no code when I connect it, so it seems to be working just fine, but it closes itself immediately when I start the car. If I disconnect it, I get the fault code and the engine works just fine.

The replacement for the new one is on its way, I just wanted to check the start of the COLD engine in another car with good ASV.
 

nord

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Well then, you're almost there. Certainly the new ASV will determine whether the fault lies within the present unit or within the circuitry. I tend to expect that your current ASV is faulty and that the motor is not fully isolated from the valve body. Your new ASV will clear up this question.

Short of the ASV being at fault there are other considerations. Since the ASV is an all or nothing unit (either open or closed), there is really no scenario where the unit should ever remain in a mid position.

You'll find four wires going to the device. Two for motor power and two to a position sensor. Spring tension will hold the valve normally open. Engine shutdown will apply voltage to activate the ASV motor, the valve shutter will cycle, and a flag will pass the sensor in order to signal to the ECU that the function has taken place... At least that's the way it should be.

If there is voltage to the motor and a ground path, you may expect the motor to cycle. If a high resistance path, then likely a partial cycle until such point as the motor is unable to overcome the homing spring.

Of course the sensor wires could also be a problem. If one or the other was crushed and partially shorted or open, then the ECU would receive spurious information and attempt to cycle the ASV based on false information.

My guess here is the ASV motor. Short of an obvious broken or shorted wire in the harness I expect the new unit will work as advertised. While your comfort level might be boosted by looking at another car, you actually have everything you need sitting right in front of you.

One suggestion before you do much of anything else... Disconnect the present unit but leave it in the intake circuit. Simply plug in the new valve and watch it cycle before you do anything else. If it works properly your problem is solved. If not, then it's diagnostic time.
 

Ol'Rattler

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The new ASV I ordered is weird: there is no code when I connect it, so it seems to be working just fine, but it closes itself immediately when I start the car. If I disconnect it, I get the fault code and the engine works just fine
It should not close when you start the car. The only time it should close is when you turn the key off, it will close for about 5 seconds and then open back up until the next time you turn off the key off.

Either you have a wiring problem, or the ASV you bought is not correct for your car or is defective. (Prothe garbage?)

Do you have VCDS? you may be able to determine what is going on by monitoring some of the measuring blocks.
 

maloosheck

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It should not close when you start the car. The only time it should close is when you turn the key off, it will close for about 5 seconds and then open back up until the next time you turn off the key off.
So even when the EGR valve opens the IMF remains fully open?

Either you have a wiring problem, or the ASV you bought is not correct for your car or is defective. (Prothe garbage?)
The wiring seems to be just fine. The PN seem to be the same (superseded version) and the manufacturer is the same (Siemens VDO).

Do you have VCDS? you may be able to determine what is going on by monitoring some of the measuring blocks.
I was checking the measuring blocks but I have not really found anything that would tell me whether the IMF is faulty or not. Is there any block that shows requested position and actual position?
 

2footbraker

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Some people have said the ASV closes partway when the EGR opens but I have never been able to find any evidence of this in VCDS. I do know that the turbo vanes close a bit when the EGR opens though.
 

nord

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One more time... The ASV is a two position valve. At rest it is forced into the open position by spring tension. When activated it closes against spring pressure. There is one sensor at the limit of closed travel. Once the flag is removed from the sensor face the ECU assumes the ASV to be fully open. That's it and that's all!
 

slamhouse

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Some people have said the ASV closes partway when the EGR opens but I have never been able to find any evidence of this in VCDS. I do know that the turbo vanes close a bit when the EGR opens though.
The ASV in the BRM motor fluctuate in throttling depending on load and speed to aid in the inhalation of exhaust gasses while cruising.

This is also where you will see the turbo vanes close slightly to raise EMP's higher than that of the intake to "push" exhaust gas into the already pressurized intake.

This valve will close fully upon engine shutdown to reduce shutdown shutter.

Upon starting the car, you may notice a slight closing action of the egr <10% but resume to fully open as the car "checks" its function.

This sounds as id an internal resistor in the assembly is shot throwing much more power to the electrical motor than desired therefore shutting it completely shortly after start-up. Or the assembly you recieved was simply defective.
 

2footbraker

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slamhouse, where did you find this info? I think I will have to side with nord (as abrasive as he is :D) on this until evidence to the contrary is found.
 

nord

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Sorry but I respectfully disagree. The ASV is a two position valve only. There is no provision for sensing anything but closed. Default is full open and the ECU interprets this position only by seeing that the flag is not over the sensor.

Any partial activation of the ASV at any time other than shutdown is cause for suspicion as there is no control mechanism in place to regulate the plate position.

Open one of these puppies up and have a look. A simple dc motor, a gearset, a plate with a flag attached, and a sensor mounted at the far end of the closed position. That's it! The ECU only calls a fault when it fails to see a close of the ASV. Really a simple mechanism without much mystery.

And to 2footbraker... Thank you for the compliment. I can't help but to be a stubborn kraut. Abrasive probably fits.:)
 
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maloosheck

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Open one of these puppies up and have a look. A simple dc motor, a gearset, a plate with a flag attached, and a sensor mounted at the far end of the closed position. That's it! The ECU only calls a fault when it fails to see a close of the ASV. Really a simple mechanism without much mystery.
I am afraid you might be wrong. There is something that looks like a piece of magnetic metal on the flap axle and there is certainly some kind of the sensor (Hall maybe?) inside the plastic cover on the opposite side to this magnet. I am still not sure if it is an analog one or just discrete (on/off) type, but I believe I saw some % in one of the measuring blocks.

As soon as I remove the faulty ASV, I will post the pictures of the stripped teeth and the rest.
 

slamhouse

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If the ASV is not throttling the motor then please do show me the other throttle plate in the intake that throttles the motor during crusing to aid in the ingestion of exhaust gases.

I do however love to be proven wrong :)
 

nord

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Total of four wires on the ASV. Two supply current to the dc motor and two to the sensor. A second sensor would require at least one more wire unless a rheostat type of arrangement. It's just not there. Look up the wiring schematic and see for yourself. One dc motor with a positive and ground totally isolated from the rest of the device. One sensor with two wires totally isolated from the motor and the valve body activated by a flag on the shutter assembly. Any continuity between motor and sensor signals a failure. Same with any continuity of either to the frame ground.

ASV is not a throttle device. Throttle is a gasoline engine term and diesels don't run that way. The ASV is an "electric potato" if you will. It's sole purpose is to assure a shutdown in both normal operation and in an emergency by shutting off intake air. Your engine will run perfectly with or without the device being operational as long as the shutter is open. The problem is that you'll face a potential runaway should the valve become disabled in the open (default) position.

In our diesels the intake air is supplied under pressure from the turbo. EGR gasses are returned to the intake circuit under pressure also as exhaust gasses are under considerable pressure. There is no need to "throttle" the intake in order to ingest EGR gasses. If you don't believe me then back off the fasteners on the EGR return pipe and give a listen. (I wouldn't, but it would prove the point.)

As to proving anyone wrong, I'm not in that business. The proof is self-evident and lies right before your eyes. You'll either see it or you won't. My only intention to lead you in the right direction as it makes no difference to me whether we agree or don't.

One of the things I've discovered over my years of VW ownership is that we tend to over-complicate things. Our cars are sophisticated on many levels, but they're also fairly simple once we accept the fact that a computer controls the functions of these vehicles to a major extent.

My profession has been in the computer field since 1966. This doesn't mean that I'm always correct, but it gives me a great deal of insight as to how a component functions when I remove and dissect a failed unit. I assure you that I've done this with the ASV as mine failed not too long ago.

I'm constantly amazed at German engineering. None of the multitude of computer controlled features on our vehicles is really cutting edge technology. The fact is that the computer just makes these features easily available. What amazes me is that engineers sat down and decided to write software to alarm for such mundane things as a blown light bulb. Sometimes I wonder if their efforts might have been better directed to such things as adding a bit more stress relief to such things as the door wiring harness.

In order to really be able to diagnose many of our problems it's necessary to understand that a gasoline and a diesel engine are different animals. They're much the same and very different all at the same time. Such things as a throttle plate don't exist on a diesel because a diesel always runs with the intake totally open.

The ASV is a prime example here. On a gasoline engine it would be considered a throttle body of sorts, but not so on our diesels. On the TDI the "throttle" assemble is considered a valve and used only for the purpose of positively shutting down the engine.

Think about what I've shared. Ask a real diesel mechanic about the differences between gas and diesel engines. They really are very different!
 

nord

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Not intended to belittle in any way. Some of your comments just led me to believe that you might misunderstand some things.

No hard feelings intended. No effort on my part to prove anything to you. And absolutely no ego on my part.
 

DPM

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Nord, you'd need to update yourself a little. I can't speak of your particular variant of PD, but many diesels absolutely DO have a throttle valve, and for the reasons alluded to by slamhouse. Both vehicles in our stable (Pug, Subaru) have throttles...
 

nord

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DPM,

In my experience diesels do not have a throttle as such. You can call it an intake restrictor. You can call it a throttle. But the fact remains that diesels have an open intake and are controlled by fueling. I'm sure there are variations for different purposes, but diesels are basically the same.

As to the Jetta with a BRM engine the ASV is as I've described. Please feel free to update me if a new ASV has been developed.
 

DPM

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today's diesels are indeed throttled in part-load operation. It can create a partial vacuum to increase EGR rate, but it's also used to enrich the burn at times- In my Subaru, Scangauge reports the throttle @78 degrees (near wide open, it goes to 90 on selftest) during normal WOT but is modulated 20-50 during warmup, and closed to a tight 5deg at idle during regens.
 

nord

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DPM,

And so a matter of semantics. I understand the theory totally but would refrain from using the term "throttle". We, however, agree upon the fact that it's a valve used to restrict intake air, don't we?

The BRM Jetta uses such a valve, but not an incremental unit. It's either full open in default mode or fully closed on shutdown. There's no provision for calibrated opening and closing on US models.

In any case I'll be the first to admit that engineers tinker with the simple diesel configuration. The use of restrictors and adjustable intakes is totally understandable. My point is that the use of the throttle term is totally misleading within the context of diesel operation as diesels are a fuel controlled engine.

My Best,

B
 

nord

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DPM,

I really don't care about the term as long as we both understand just how this valve is used on our cars. The following will set the record straight in that you are correct about the term's use in this situation. As long as we agree that the "throttle" is not used to regulate engine power I think we'll be OK.

Humor me if you will...

Throttle

From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the control of engine power. For other uses, see Throttle (disambiguation).
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (i.e., by the use of a throttle), but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which the power or speed of an engine is regulated. What is often termed a throttle (in an aviation context) is more correctly called a thrust lever. For a steam engine, the steam valve that sets the engine speed/power is often known as a regulator.
Contents



Internal combustion engines


A cross-section view of a throttle valve


In a gasoline internal combustion engine, the throttle is a valve that directly regulates the amount of air entering the engine, indirectly controlling the charge (fuel + air) burned on each cycle due to the fuel-injector or carburetor maintaining a relatively constant fuel/air ratio. In a motor vehicle the control used by the driver to regulate power is sometimes called the throttle pedal or accelerator.
The throttle is typically a butterfly valve. In a fuel-injected engine, the throttle valve is placed on the entrance of the intake manifold, or housed in the throttle body. In a carbureted engine, it is found in the carburetor.
When a throttle is wide open, the intake manifold is usually at ambient atmospheric pressure. When the throttle is partially closed, a manifold vacuum develops as the intake drops below ambient pressure.
Usually the throttle valve is controlled with a throttle pedal or lever via a direct mechanical linkage. In vehicles with electronic throttle control, the manual throttle control sends a signal to the Engine Control Unit (ECU), which then directly controls the position of the throttle valve. This means that the operator does not have direct control over the throttle valve; the ECU can finely control the valve in order to reduce emissions or maximize performance.
In a reciprocating-engine aircraft, the throttle control is usually a hand-operated lever or knob. It controls the engine power, which may or may not reflect in a change of RPM, depending on the propeller installation (fixed-pitch or constant speed).[1]
The power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder. Because the engines do not need to control air volumes, they lack a butterfly valve in the intake tract. An exception to this generalization is newer diesel engines meeting stricter emissions standards, where a throttle is used to generate intake manifold vacuum, thereby allowing the introduction of exhaust gas (see EGR) to lower combustion temperatures and thereby minimize NOx production.
Throttle body


The components of a typical throttle body


In fuel injected engines, the throttle body is the part of the air intake system that controls the amount of air flowing into the engine, in response to driver accelerator pedal input in the main. The throttle body is usually located between the air filter box and the intake manifold, and it is usually attached to, or near, the mass airflow sensor.
The largest piece inside the throttle body is the throttle plate, which is a butterfly valve that regulates the airflow.
On many cars, the accelerator pedal motion is communicated via the throttle cable, to activate the throttle linkages, which move the throttle plate. In cars with electronic throttle control (also known as "drive-by-wire"), an electric motor controls the throttle linkages and the accelerator pedal connects not to the throttle body, but to a sensor, which sends the pedal position to the Engine Control Unit (ECU). The ECU determines the throttle opening based on accelerator pedal position and inputs from other engine sensors.

Throttle body showing throttle position sensor. The throttle cable attaches to the curved, black portion on the left. The copper-coloured coil visible next to this returns the throttle to its idle position when the pedal is released.


When the driver presses on the accelerator pedal, the throttle plate rotates within the throttle body, opening the throttle passage to allow more air into the intake manifold. Usually an airflow sensor measures this change and communicates with the ECU. The ECU then increases the amount of fuel being sent to the fuel injectors in order to obtain the desired air-fuel ratio. Often a throttle position sensor (TPS) is connected to the shaft of the throttle plate to provide the ECU with information on whether the throttle is in the idle position, wide-open throttle (WOT) position, or somewhere in between these extremes.
Throttle bodies may also contain valves and adjustments to control the minimum airflow during idle. Even in those units that are not "drive-by-wire", there will often be a small electric motor driven valve, the Idle Air Control Valve (IACV), that the ECU uses to control the amount of air that can bypass the main throttle opening.

Image of BMW S65 from the e92 BMW M3 showing eight individual throttle bodies


Many cars have a single throttle body. Others employ more than one, chained together by linkages to improve throttle response. At the extreme, high performance cars like the E92 BMW M3 and high performance motorcycles like the Yamaha R6 use a separate throttle body for each cylinder, often called "individual throttle bodies" or ITBs.
A throttle body is somewhat analogous to the carburetor in a non-injected engine. Carburetors combine the functionality of the throttle body and fuel injectors into one in order to modulate the amount of air flow and to combine air and fuel together. Cars with throttle body injection (called TBI by General Motors and CFI by Ford) locate the fuel injectors in the throttle body, thereby allowing an older engine to be converted from carburetor to fuel injection without significantly altering the engine design.
Other engines

Most engines have some kind of throttle control, though the particular way that power is regulated is often different.
Liquid rockets are throttled by controlling the pumps that send liquid fuel and oxidizer to the combustion chamber. Solid rockets are not controllable once their solid fuel is ignited. Hybrid rockets, like the one used in Space Ship One, use solid fuel and liquid oxidizer; thus, throttling is possible through the oxygen pumps, as in a full liquid rocket motor.
In a jet engine, engine output is also directly controlled by changing the amount of fuel flowing into the combustion chamber, usually with an autothrottle. In some instances, a "throttle" is known as a "thrust lever" (as in most Airbus and Boeing aircraft). This is chiefly due to the fact that "throttle" is associated with traditional gasoline engines.[2]
 

slamhouse

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L
The ASV in the BRM motor fluctuate in throttling depending on load and speed to aid in the inhalation of exhaust gasses while cruising.

This is also where you will see the turbo vanes close slightly to raise EMP's higher than that of the intake to "push" exhaust gas into the already pressurized intake.

This valve will close fully upon engine shutdown to reduce shutdown shutter.

Upon starting the car, you may notice a slight closing action of the egr <10% but resume to fully open as the car "checks" its function.

This sounds as id an internal resistor in the assembly is shot throwing much more power to the electrical motor than desired therefore shutting it completely shortly after start-up. Or the assembly you recieved was simply defective.
Thanks for the fun pissing contest about how I used the word throttle to describe the action that the asv plays.

Lets leave it at my original reply to the OP and get back on topic :)
 

maloosheck

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So another IMF arrived today and this one works as expected: open while engine running and closes only when the engine is shut off.

One MIL off :D.
 
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