Car won't start? Check your Anti Shudder Valve

[compu_85]

In the chat room, there have been a couple of guests whose cars would not start because the anti shudder / intake changeover valve was stuck closed. I'm writing this so that people not familiar with the shudder valve can see if it is stuck from looking at it.


On the passenger side of the engine, looking on the side next to the firewall you'll see this:



The black plastic arm to the left of the round silver thing is what operates the shudder valve. This is a throttle plate which closes completely, preventing air from getting into the engine. It closes when you turn the key off to make shutdown smoother, and as a backup way to kill the engine. If it should get stuck closed, the engine will not start, as it can't get air.



In this picture, I'm holding the valve closed with my finger. Notice how the metal bit is pointing straight up now, and you can't see the top of the diaphragm on the dashpot anymore?


Here are some closer pictures:

Open (engine can start):



Closed (engine can't start):



Again, notice how the metal bit is pointing up now?

If the valve is stuck, try pulling up where you see me pushing down. It should spring back to the open position.

If you take the rubber elbow off from the intake and look in, you will probably see lots of black goop:



Don't scrape this out when the intake is attached to the engine as some could fall in, and get stuck inside, and bend a valve. That will ruin your day. Refer to the intake manifold cleaning procedures found elsewhere on the forums. This picture also shows the valve open... it's the flat round bit with the layer of gunk on top.

This info only applies to the ALH engine found in 1998-2003 Beetles, and 1999.5-2003 Golfs and Jettas. The A3/B4 (96-99) cars don't have this valve, and on the 04+ (PD) cars, it's moved by an electric motor, and actually closes some while the engine is running to draw in more EGR. It's theorized that this flap getting stuck or remaining closed is what causes the hesitation on the 2.0 PD engines found in the 04 and 05 Passats.

If you have checked this, and the valve is open, and the car also stalls sometimes when your driving, consider checking your Relay 109, which supplies power to the engine computer and is known to fail. If the glow plug light does not come on then go out when you turn on the ignition, this relay has likely failed.

Hope someone finds it useful!

-Jason

[ColoradoRich]

Well, last night my Tdi died and I had to have it towed to my local repair shop (about 12 miles). I thought I might have a battery problem but later thought it might be a fuel filter problem. THEN ... this morning I did a search on this forum and found this link. I went to the repair shop (which, fortunately was still closed) and pulled the "anti shudder valve," which was stuck in the "in" position.
It started immediately! Whew! I had visions of having to have it towed again to a local stealership.
Thank you so much for taking the time to post those pictures to SEE what you are talking about. Our language has it's limits with describing auto parts and locations.
Coloradorich
Tdi Golf, 2001, 160,000 miles.

[whitedog]

Great pictures. Many times people will say that their car won't start when warm and this is very often the problem, correct?

Or they say their car won't restart after shut down.

Planning on linking this in the How-to section?

[KansasTDI]

This happened to me this morning.
Car would try to start for brief second and then just cranking the engine.
I appreciate the help from all of the board members.

[bhtooefr]

Link it in the how to section, and I'm nominating this thread for sticky status.

[LarryLymb]

I have noticed a couple of similar starting problems. One, sometimes if I immediately try to start the car before the computer has had time to run thru its start up procedures, the car won't start. And two, sometimes if I insert the key upsidedown (with the key holder slot towards the top) the immobilizer icon lights up on the dash and the engine will start but immediately die. Anyone else notice either of these symptoms?

[jasonTDI]

You can cure the problem temporarily so you don't have to unstick it by cutting the vacuum line to it. The long term cure is to clean the intake and EGR.

[compu_85]

Don't try to pull the vaccuum line off the dashpot, you will break the nipple off, like I did, and end up rebastardizing it on. (see the glue in the pictures?)

Oh, and I allready put a link to this in the how-to section... but its on page 2...

-J

[jasonTDI]

That's why I said to CUT it! Couple it together or use a new line once you carefully cut it off the nipple when it's OUT of the car.

[compu_85]

Exactly! Just wanted make the point doubly clear... "Oh, he says to remove the line... I bet I can just pull it off... "

[jasonTDI]

You just know someone is going to be like "you said to pull it!" Waaahhh!!!! Numbskulls!

[ronenb]

I have a 1998 Beetle TDI 5 speed and have a problem with the car reving up past 1200-1300 rpm's. If I let the car the car idle for 12/hr to 45 mins. it runs fine. However, the next moring the car won't rev up again and can't get to even speeds of over 20 MPH. If I try to rev up the car higher than 1200 the motor stutter and smokes black smoke very bad, but when I release the gas peddal the car resumes to idle perfectly. Since developing this problem I have tried replacing the fuel filter, air filter, fuel shut off valve with not results. Please help.

Thank you in advance,
Ron

ronenb@aol.com

[bhtooefr]

Bumping this thread so it's easy to find.

[lance71137]

Can some one please give me a link to the "how to" section that Jason is talking about.
Thanks,

Lance

[compu_85]

It's the HOW TOs thread, stickied at the top of this forum. Here is a link.

-J