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vacilador
Samba Member
Joined: May 05, 2015
Posts: 21
Location: portland, or
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 Posted: Mon Feb 05, 2018 11:11 pm Post subject: engine won't stop. Throttle valve? |
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1974 Type 2 Bay Window
Earlier tonight I was accelerating to catch up to this girl driving in the right hand lane... so I pushed down on the accelerator and slowly but surely I caught up to her.
But then as I was trying to coast, and pulled my foot off the accelerator, the engine didn't stop ...
The accelerator pedal isn't stuck. Maybe the throttle is stuck open ... not sure
Was able to fudge my way home turning off the car and braking.
Thought someone on the Samba might be able to describe a fix or
a process to figure out a fix for this sort of predicament.
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1974 VW Bay Window Automatic Fuel Injected
2002 VW Passat V6 |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12722
Location: on a bike ride somewhere
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| Posted: Tue Feb 06, 2018 3:04 am Post subject: Re: engine won't stop. Throttle valve? |
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How familiar are you with your engine compartment? If you know where your throttle arms and cross-bar are, you should check to make sure the throttle return mechanism is in place. All US cars after 1972 must have two independent throttle return mechanisms, so most dual carb setups use a spring on each carb and one spring on the linkage. Single center-mount carbs usually get one spring on the carb and another pulling the throttle arm back anchored somewhere hokey.
Check that the throttle mechanism(s) move freely and get back to us!
Robbie
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 22668
Location: NYC/Upstate/ROW
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| Posted: Tue Feb 06, 2018 4:47 am Post subject: Re: engine won't stop. Throttle valve? |
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I never knew that regulation , Robby....I wonder how electronic modules cover that. Does the vacuum pull off on later beetle engines count as the second system!
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue Feb 06, 2018 8:40 am Post subject: Re: engine won't stop. Throttle valve? |
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I'll bet that impressed her - "Help I can't stop....."
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busman78
Samba Member
Joined: August 17, 2004
Posts: 4523
Location: Oklahoma City, OK
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| Posted: Tue Feb 06, 2018 9:14 am Post subject: Re: engine won't stop. Throttle valve? |
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| Important lesson, do not stock women with your VW bus! |
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vacilador
Samba Member
Joined: May 05, 2015
Posts: 21
Location: portland, or
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| Posted: Tue Feb 06, 2018 4:14 pm Post subject: Re: engine won't stop. Throttle valve? |
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So this afternoon I started up the engine....
Engine power seemed normal at first, then gradually powered up and up and up by itself.
(I am not yet familiar with the engine compartment). I opened the rear hatch and I believe I did find the throttle arm mechanism.
I was able to rotate it (with my hand) towards the stopper, which did depower the engine quite a bit.
This seems too easy.... and I only found one throttle mechanism if indeed this is the right part (photo attached)
Thoughts?
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1974 VW Bay Window Automatic Fuel Injected
2002 VW Passat V6 |
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timvw7476
Samba Member
Joined: June 03, 2013
Posts: 2205
Location: seattle
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| Posted: Tue Feb 06, 2018 5:45 pm Post subject: Re: engine won't stop. Throttle valve? |
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that melted debris on the throttle plate return spring would make
me suspect the return spring has lost it's temper.
Just an idea. |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12722
Location: on a bike ride somewhere
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| Posted: Wed Feb 07, 2018 1:26 am Post subject: Re: engine won't stop. Throttle valve? |
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| vacilador wrote: |
Thoughts? |
Thoughts?
Yes! You have the exceedingly rare 1974 fuel injection system. I didn't even consider (in my original post) that you would have this system, since we only get one or two posts a year regarding it on here.
I've posted a picture below of what I think you have as a mechanical "deceleration valve…" But for now, can you confirm (with a helper) that when you fully release the gas pedal from half-pressed-down, that the throttle body (in your picture) fully returns to idle? Or can you get the throttle body to return more by pressing the tab to the right in your picture?
Robbie
1974-only decel valve:
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airschooled
Air-Schooled
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| Posted: Wed Feb 07, 2018 1:31 am Post subject: Re: engine won't stop. Throttle valve? |
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Oops- forgot to attach this photo. Here is your throttle arm. Move it the following ways by hand to make sure your cable isn't binding. Does this slow the idle down?
Robbie
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williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Wed Feb 07, 2018 3:07 am Post subject: Re: engine won't stop. Throttle valve? |
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Also- you might try turning the return spring round so the straight part of the spring is on the throttle and the coils are above the plenum. put some "triflone" spay on all that monkey motion - you may have a sticky shaft somewhere.
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some days I get up and just sit and think. Some days I just sit.
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12722
Location: on a bike ride somewhere
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| Posted: Wed Feb 07, 2018 3:09 am Post subject: Re: engine won't stop. Throttle valve? |
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| williamM wrote: |
| Also- you might try turning the return spring round so the straight part of the spring is on the throttle and the coils are above the plenum. |
Oooh good catch; the coils being near the throttle pivot could bind and hold the throttle open.
Robbie
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50348
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| Posted: Wed Feb 07, 2018 4:39 am Post subject: Re: engine won't stop. Throttle valve? |
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Looks to me like you need to do some housekeeping in there. There is shredded debris laying everywhere and signs of fire. A review of the "FIRE" sticky might give you a clue as to what will happen to an old vehicle that is not being properly maintained. Also read up on replacing rubber fuel lines.
Note: Women aren't very impressed by the charred remains of classic vehicles found sitting by the side of the road. |
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williamM
Samba Member
Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Wed Feb 07, 2018 8:24 am Post subject: Re: engine won't stop. Throttle valve? |
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| Wildthings wrote: |
Note: Women aren't very impressed by the charred remains of classic vehicles found sitting by the side of the road. |
They may not be impressed, but you could be in line for a sympathy cuddle-- or more.
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some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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vacilador
Samba Member
Joined: May 05, 2015
Posts: 21
Location: portland, or
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| Posted: Wed Feb 07, 2018 3:44 pm Post subject: Re: engine won't stop. Throttle valve? |
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Good news. At least for now, the throttle mechanism is returning to idle on it's own and the cable is pulling freely.
I pressed the tab to the right to orient the mechanism to idle and dropped tri-flow at the high point of the mechanism which cascaded down the inner depths I could not reach with the tip of the applicator on the bottle.
Sending a pic so you can see the whole apparatus.
I also cleaned up the debris a bit.
Soon I will look into replacing fuel lines.
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1974 VW Bay Window Automatic Fuel Injected
2002 VW Passat V6 |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50348
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| Posted: Wed Feb 07, 2018 4:20 pm Post subject: Re: engine won't stop. Throttle valve? |
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New S-boots (the big shoddily repaired S shaped hose) are available if yours take the same as used in later years.
Make sure the fuel hose you buy is rated for FI use. US spec hose should say 30r9 on it somewhere, while European hose has its own ratings which aren't as straight forward, at least to me.
Last edited by Wildthings on Thu Feb 08, 2018 8:58 am; edited 1 time in total |
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airschooled
Air-Schooled
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Location: on a bike ride somewhere
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| Posted: Thu Feb 08, 2018 1:49 am Post subject: Re: engine won't stop. Throttle valve? |
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| Wildthings wrote: |
| New S-boots (the big shoddily repaired S shaped hose) are available if yours take the same as used in later years. |
I don't think the '74-only S-boots are available. Apparently the PO didn't either… 
Robbie
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21519
Location: Oklahoma City
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| Posted: Thu Feb 08, 2018 8:30 am Post subject: Re: engine won't stop. Throttle valve? |
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| asiab3 wrote: |
| vacilador wrote: |
Thoughts? |
Thoughts?
Yes! You have the exceedingly rare 1974 fuel injection system. I didn't even consider (in my original post) that you would have this system, since we only get one or two posts a year regarding it on here.
I've posted a picture below of what I think you have as a mechanical "deceleration valve…" But for now, can you confirm (with a helper) that when you fully release the gas pedal from half-pressed-down, that the throttle body (in your picture) fully returns to idle? Or can you get the throttle body to return more by pressing the tab to the right in your picture?
Robbie
1974-only decel valve:
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This is not a deceleration valve.....per-se. A deceleration valve.....generally.....operates on over run with throttle closed at higher rpms. This one works in a very specific range just above idle.....and is not an emissions device. Its a drivability device.
It came originally from the 411 and 412. Until I bothered toook in my bus books....  ....about a year and half ago....I had not realized they continued it into the bus for a period of time. It came on the vw 411 starting in about 1970 I think. I wrote a bit about it a year ago....how to adjust. I will post a link when I find it.
It is for the automatic transmission. Most of us call it the "throttle kicker" or throttle positioner.
Its purpose is to kick the throttle open a very small amount as you are coming to a stop with your foot off the throttle......because there is a very short period of time and transmission rpm where the torque converter has not yet bled off enough internal pressure to "de-couple"......and it can drag the engine rpm down enough to almost stall.
This prevents that.....WHEN its operating properly. It has several potential issues.
1. It is VERY sensitive to vacuum leaks, engine condition (meaning age and vacuum signature related to wear and compression)
2. It is very sensitive to adjustment.....and its adjustment will never be right unless idle is steady and vacuum is perfect.
3. It has small vacuum leak issues with age.
If the OP has vacuum leaks either in the line between manifold and the kicker or in the center intake manifold itself.....this unit can easily cully extend....and prevent the throttle from closing.....causing some or all of the problem he is experiencing.
The other thing to look for on that type of TB....with the axial positive return spring wound arround the throttle shaft....is that it has a shaft seal in both top and bottom. If those are chewed up....not only do they leak vacuum they gum up the throttle shaft and can keep it from fully closing. Ray |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50348
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| Posted: Thu Feb 08, 2018 9:02 am Post subject: Re: engine won't stop. Throttle valve? |
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| asiab3 wrote: |
| Wildthings wrote: |
| New S-boots (the big shoddily repaired S shaped hose) are available if yours take the same as used in later years. |
I don't think the '74-only S-boots are available. Apparently the PO didn't either…
Robbie |
Don't think I have ever seen the California '74 fuel injection setup, I guess it might share some additional parts with the '74 412? What if one used a later air cleaner housing, would that allow for the use of the later S boot? |
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 22668
Location: NYC/Upstate/ROW
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| Posted: Thu Feb 08, 2018 9:12 am Post subject: Re: engine won't stop. Throttle valve? |
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I think all that Shoe Goo on the throttle body will almost guarantee things are sticky and binding.
Im guessing 74 FIJ parts are are gold capped hens teeth in paucity, though
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williamM
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Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Thu Feb 08, 2018 9:59 am Post subject: Re: engine won't stop. Throttle valve? |
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You should really get the right throttle spring in there though
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some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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