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Old March 31st, 2010, 18:25   #1
steelmb
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Default Runaway/Anti-Shudder Valve

I drive a 2003 Jetta Wagon TDI. To my knowledge it is completely stock. I love the car and have always been concerned about the consequences of a runaway since I care for the car very well and I intend on keeping the car for an extended period of time.

I read every post that I see regarding runaways and how to stop them. Through this reading I had come to the disappointing conclusion that VW engineers had dropped the ball and not set things up properly to shut the engine down in event of a runaway even though everything (anti-shudder valve) was in place to do so. I eventually set out to confirm this by watching the anti-shudder valve as the engine was shut down. It appeared that my fears were confirmed as the valve only closed for 2 seconds or less which would not be sufficient to shut down a full blown runaway in my opinion.

I began devising a plan to have the anti-shudder valve stay closed longer upon shutting the key off to solve this. I was pretty much ready to start acquiring the parts to do it when I ran across this post. http://forums.tdiclub.com/showthread.php?t=276398 Posts #11 and #12 by Ski in NC were the ones that really peaked my interest. Could it be possible that the VW engineers had not dropped the ball?

Well the weather was reasonably warm today and I had some time so I set out to see if I could duplicate Ski in NC's findings. I back probed the N239 (anti-shudder valve control solenoid) electrical connector and lead wires into the cabin which I connected to my volt meter to. I started the engine and my meter read 24 mv which is negligible. I headed out of town a couple miles to a nice steep hill and as I crested the hill I shut down the engine and left it coast in gear to keep the engine turning with the key off. The volt meter went to 13.58 volts showing that the anti-shudder valve was actuated. The meter stayed at 13.58 volts for well over a mile as the car slowed down. Eventually when the car was going slow enough that it was just about to stop I pushed in the clutch and the engine stopped turning. within about a second the meter went to 0 volts. I figure the valve was actuated for about 1.5 min. Certainly long enough to stop a runaway! I tried it a second time with the same result.

From this I conclude that if a person maintains the anti-shudder valve system and keeps it in good working order that it will indeed shut down a runaway and help prevent engine/bodily damage. Anyone who has had a runaway that they were unable to shut down with the key also had a problem with their anti-shudder valve. Joester in post #16 of this thread http://forums.tdiclub.com/showthread.php?t=273249 is completely wrong provided the anti-shudder valve a ECU are operating correctly.
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Old March 31st, 2010, 18:33   #2
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so the ecu must trigger it in consideration of rpm?
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Old March 31st, 2010, 18:59   #3
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Quote:
Originally Posted by steelmb
Joester in post #16 of this thread http://forums.tdiclub.com/showthread.php?t=273249 is completely wrong provided the anti-shudder valve a ECU are operating correctly.
gee thanks. Lol

no but those are some great results. German engineering ftw!

Then why do unstoppable runaways happen? Not everyone has an egr delete...
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Old March 31st, 2010, 19:05   #4
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Most people that experience runaway have modified engines anyway. So I'll venture the guess that the ASV and EGR have been removed in most cases.
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Old March 31st, 2010, 19:30   #5
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Quote:
Originally Posted by Joester
gee thanks. Lol

no but those are some great results. German engineering ftw!

Then why do unstoppable runaways happen? Not everyone has an egr delete...
I wasn't really picking on you Joester as many have said that the AS valve would not shut down a runaway. Your post in that thread was so enthusiastic that I just had to use it. LOL. Sure did not take you long to find this thread.
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Old March 31st, 2010, 19:44   #6
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No offense taken. I'm wrong a lot. =P

Oh and I use the "view new posts" feature soo...
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Old April 4th, 2010, 08:06   #7
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In my defense: http://forums.tdiclub.com/showthread.php?t=278408
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Old April 4th, 2010, 11:15   #8
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Quote:
Originally Posted by Joester
There is nothing there that indicates his anti-shudder valve was operating correctly. I am glad you pointed that thread out though as there seems to be a lot of misinformation on the subject. I wonder how many people have malfunctioning anti-shudder valves and do not even realize it? The problem will only create subtle shutdown symptoms that have no effect on drive-ability and if someone is not the original owner they may think those symptoms are normal. The problem only really raises it's ugly head in the case of a runaway.
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Old April 4th, 2010, 11:33   #9
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The automatic 2002 New Beetle in the shop now had an inoperable Anti Shudder VAlve ASV, until I fixed it.

I really appreciate you guys (Ski and Steel) for following up on this issue. I had hoped that it had the design features that you found it did have.

The ALH VCDS Output Tests does not test the ASV' capability to shutdown the engine. The PD ASV is tested as part of the VCDS Output tests.
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Old April 9th, 2010, 16:02   #10
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Well then that makes 2 folks who have verified the ASV does stay activated as long as the engine is still turning. That is good news for those of us who still have their EGR's. I certainly don't live in daily fear of a runaway but those who are running on spotty turbos, etc. it would pay to check your ASV for proper function. If you can't afford a turbo yet, at least pony up and fix your ASV if needed. Good info steelmb...
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Old June 8th, 2010, 06:30   #11
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I have a 2001 Jetta TDI . I experienced a engine runaway condition last week. Turning off the key shut down the engine in my case. The engine reved during a shift and I didn't complete the shift. The engine ran away: I pulled over to the side of the road and turned the key off and the engine shut down.

After all the reading I realized I should have engaged 5th gear and then pulled over. I hope if it ever happens to me again to have the presense of mind to do what I need to do. I was lucky this time. I didn't destroy the engine.
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Old June 8th, 2010, 07:22   #12
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Quote:
Originally Posted by MicroRacer
I have a 2001 Jetta TDI . I experienced a engine runaway condition last week. Turning off the key shut down the engine in my case. The engine reved during a shift and I didn't complete the shift. The engine ran away: I pulled over to the side of the road and turned the key off and the engine shut down.

After all the reading I realized I should have engaged 5th gear and then pulled over. I hope if it ever happens to me again to have the presense of mind to do what I need to do. I was lucky this time. I didn't destroy the engine.
Did you find and fix the cause of the runaway?
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Old June 8th, 2010, 07:37   #13
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So, if I do an EGR cooler delete and have the EGR 'turned down' [the guru used better words to describe this.] would that negatively affect my ability to kill a runaway engine?
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Old June 8th, 2010, 08:55   #14
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No as long as you leave the ASV/EGR valve in place and do not replace it with a race pipe. This of course assumes that your ASV is operating correctly.
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Old June 8th, 2010, 11:07   #15
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I have started checking the ASV operation on every ALH that I check out now.
Manually finger (easily done with one finger) the ASV and verify the engine quickly dies. This ensures that it is not blocked open with crud.
Then observe the ASV as the operator shuts down the engine and verify that it operates.
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