1976 Bus - Test for AFM? ** It's still bucking!!**

Carbs & F.I.

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vdubyah73
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Post by vdubyah73 » Fri Jul 24, 2009 9:43 am

you found it! I've done the same thing and have seen others do it as well. it's usually one of the first places I look on other peoples cars. Sometimes people are afraid of over tightening and go to the opposite extreme, or in my case, when it happened to me, I simply forgot to finish tightening the intakes. Distractions, getting called away in the midst of assembly cause these mistakes.
1/20/2013 end of an error
never owned a gun. have fired a few.

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Amskeptic
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Post by Amskeptic » Fri Jul 24, 2009 9:45 am

TrollFromDownBelow wrote: intake manifolds were uber loose ...

. . . . . . . . . . . . :cyclopsani: . . . . . . . . . . .
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Post by vwlover77 » Fri Jul 24, 2009 6:07 pm

:cheers: :cheers: :cheers: :cheers: :cheers:

Victory!!!! Perseverance pays off!
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

TrollFromDownBelow
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Post by TrollFromDownBelow » Fri Jul 24, 2009 9:33 pm

Still bucking...not as bad as it was last week, but still bucking. hmmph. However, it does not buck under hard acceleration, or at low speeds, and I've noticed it will buck as violently down a hill on the expressway ... almost seems more so than up the hill. Or anything above 65mph.

I'm thinking since it bucks down a hill, probably not fuel related, but maybe ignition?!?

I really want to get this resolved by next weekend... wanna go to dixie bus in OH!!
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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Amskeptic
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Post by Amskeptic » Sun Jul 26, 2009 9:44 am

TrollFromDownBelow wrote:Still bucking...not as bad as it was last week, but still bucking. hmmph. However, it does not buck under hard acceleration, or at low speeds, and I've noticed it will buck as violently down a hill on the expressway ... almost seems more so than up the hill. Or anything above 65mph.

I'm thinking since it bucks down a hill, probably not fuel related, but maybe ignition?!?

I really want to get this resolved by next weekend... wanna go to dixie bus in OH!!
Tell you what . . . tightening the nuts might not have been the Final Solution. If they have been chronically loose, you really want to pull the runners and mill the flange surfaces of the runners flat with a sandpaper-mirror deal or a good flat file.

You can check to see if you did indeed cure the intake leaks by making sure that the engine is running leanish, and spraying WD-40 (or more carefully, GumOut) on the intake-to-head surfaces. Also spray the injector seals if they have not been replaced in some time.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

TrollFromDownBelow
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Post by TrollFromDownBelow » Sun Jul 26, 2009 5:28 pm

Amskeptic wrote: Tell you what . . . tightening the nuts might not have been the Final Solution. If they have been chronically loose, you really want to pull the runners and mill the flange surfaces of the runners flat with a sandpaper-mirror deal or a good flat file.
I may have to do that. Yesterday, just to eliminate any other potential gremlins, I replaced the wires, cap, rotor, and plugs and JB welded an exhaust stud in place of the one which fell out b/c the whole is stripped... of course, still bucking! :diabloanifire:
Amskeptic wrote: You can check to see if you did indeed cure the intake leaks by making sure that the engine is running leanish, and spraying WD-40 (or more carefully, GumOut) on the intake-to-head surfaces. Also spray the injector seals if they have not been replaced in some time.
Colin
It's funny - I used more than one whole can of starter fluid to check for vacuum leaks, and not once did I get an uptick in idle when I squired some around the base of the manifold or the injector seals. The way I found it was by the high pitched squeal it was making.

I was hell-bent on getting this figured out before you get here in a few weeks. I've spent a HECK of a lot of time on this thing this summer... to the detriment of other things. All I wanted was something I could do 70mph on the freeway and get some respectible mpg to do some weekend camping. Instead I have a bus that won't do above 60mph, and I'm lucky to get 15mpg at that snails pace. It was fun and challenging, now it's become a chore. :pale: Sorry for the vent.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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vwlover77
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Post by vwlover77 » Sun Jul 26, 2009 6:00 pm

If it's any consolation, my Westy gets only 18mpg, no matter what. Drive it reasonably around town: 18mpg. Drive it steady at 65mph on the highway: 18mpg.

Can you catch some video with your digital camera while the bucking is going on? Can it be heard, or only felt?

You need to contact Keith over on the leakoil.net forum. He's in the Detroit area and may be able to offer some help, or at least a shoulder to cry on! (His username on the forum is simply "Keith"). He also has a brand new Kyle FI harness that he might be talked into letting you try out, although I think it's for the later AFM and may not fit with yours.
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

vdubyah73
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Post by vdubyah73 » Sun Jul 26, 2009 7:18 pm

Probably need new intake gaskets on the phenolic spacers between the heads and manifolds. Not hard to do, pull manifolds off, scrape old gasket sealanr off the spacers with a razor scraper. Buy some fairly thick gasket paper, something that is 1/16th to 1/8th in thick and cut your own. you need a top and bottom for each side.

This is FI right?
1/20/2013 end of an error
never owned a gun. have fired a few.

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Post by TrollFromDownBelow » Sun Jul 26, 2009 7:43 pm

I'd be happy with 18mpg. With the original engine I was getting 21-22 mpg.

I ordered some new spacers/gaskets from bus depot ... looks like its got some gasket like material already attached to it. Going to order some injector seals as well; might as well do it while I'm in there.

As far as the symptoms are concerned, not something you hear, but feel, the whole bus will lurch/jerk/buck. Since I've already replaced:

coil
points
condensor
cap
rotor
wires
plugs

I don't think it's ignition. Based on what I see with my timing light, distributor is functioning properly as well too.

Based on how the engine runs, I still think it's caused by a lean running condition feels like it is starving for fuel. I'm either sucking air, or my fuel pump is not flowing enough (haven't run that test yet) however I do have a steady 32-33psi at idle, and 35-36 psi at high rpm, no load.

What's crazy, is that I'm getting 18 inches of manifold pressure at idle...that's a decent number, you'd think if I had a a vac leak that was big enough to have such a significant impact on how it runs, I'd have lowe manifold pressure numbers.
Thanks for the words of encouragement!

As a post script, the engine IS running better ... hard start problem is almost gone (don't think my cold start valve is operating correctly).Engine idles smoother.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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Gypsie
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Post by Gypsie » Sun Jul 26, 2009 7:53 pm

According to a fairly reliable source these vanagons rolled off the factory floor with a high of 16mpg.

I agree with the get your surfaces flat and change the gaskets. Just get new blocks with gaskets on em. a few bucks but maybe less bucks....nyuk nyuk nyuk.

The loose intakes may have helped some leak channels form in one way or another.

Before you disassemble though just take another look at your mix.

Have you been making changes to your AFM? now that you have 'improved' the intake function you may have the highend mix off from the low end.. or vice versa
So it all started when I wanted to get better gas mileage....

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Post by TrollFromDownBelow » Sun Jul 26, 2009 8:26 pm

Gypsie wrote: Before you disassemble though just take another look at your mix.

Have you been making changes to your AFM? now that you have 'improved' the intake function you may have the highend mix off from the low end.. or vice versa
Was makin' changes ALL over the board. However, the wiper contact area was pretty worn - Colin recommended I get one 'eventually' that was four years ago, so figured it was time now. Installed a new one abt two weeks ago. Have not touched the settings, yet. I should be able to get it to run decent with fact settings. Once it's running decent, and I know i have all known issues fixed, then she'll get richened up a bit.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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Amskeptic
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Post by Amskeptic » Mon Jul 27, 2009 10:11 am

TrollFromDownBelow wrote:
Amskeptic wrote: making sure that the engine is running leanish, and spraying WD-40
It's funny - I used more than one whole can of starter fluid to check for vacuum leaks, and not once did I get an uptick in idle when I squirted some around the base of the manifold or the injector seals. The way I found it was by the high pitched squeal it was making.
If the mixture is already all that the engine wants, then additional fuel via starting fluid or WD-40 is not going to make a difference in idle speed or it may even make the idle drop a little. You have to make the engine WANT your leak checking sauce.

I understand that this is frustrating, but it is the character of primary learning to sorely test your patience.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

TrollFromDownBelow
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Post by TrollFromDownBelow » Mon Jul 27, 2009 6:26 pm

Amskeptic wrote: If the mixture is already all that the engine wants, then additional fuel via starting fluid or WD-40 is not going to make a difference in idle speed or it may even make the idle drop a little. You have to make the engine WANT your leak checking sauce.
Light bulb just went off - I have already marked the afm with the stock settings, so will lean up a tad and try the starter fluid thing
Amskeptic wrote: I understand that this is frustrating, but it is the character of primary learning to sorely test your patience.
Colin
What I'm frustrated with is the amount of time ... I've invested way more hours than I should have in what is consider a hobby. However, this bus is more than a hobby to me. It's a symbol of my freedom. I figure once I get it running right, I can jump into it whenever I want, say heck to the world and disappear into the woods or whatever. Besides, it's really fun to drive as a DD in the summer.

The challenge I like ... just wish I was more efficient at diagnosing and fixing. ::trollatwork::
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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Gypsie
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Post by Gypsie » Tue Jul 28, 2009 12:56 am

TrollFromDownBelow wrote:What I'm frustrated with is the amount of time ... I've invested way more hours than I should have in what is consider a hobby. However, this bus is more than a hobby to me. It's a symbol of my freedom. I figure once I get it running right, I can jump into it whenever I want, say heck to the world and disappear into the woods or whatever. Besides, it's really fun to drive as a DD in the summer.

The challenge I like ... just wish I was more efficient at diagnosing and fixing. ::trollatwork::
The destination is nice for the freedom it represents, but don't forget that the journey covers more ground and has lots of scenery...

It's getting close I can feel it.
So it all started when I wanted to get better gas mileage....

TrollFromDownBelow
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Post by TrollFromDownBelow » Wed Nov 04, 2009 9:40 pm

FWIW - Finally solved it when Colin came to town in Sept. It was most likely a poor ground at the double relay, a very loose S boot clamp (must have forgotten to retighten while I was doing all of the trouble shooting). Other possibilities were a bad Injector seal or bad intake gaskets.

Moral of this story is that many not so obvious places to have a vacuum leak, and don't rule out poor grounds/electrical connections.

Since Colin came to town I've taken it on two long one day jaunts ... one was 150 miles, the other over 200. Ran great on both.
1976 VW Bus aka tripod
FI ...not leaky, and not so noisy...and she runs awesome!
hambone wrote: There are those out there with no other aim but to bunch panties. It's like arguing with a pretzel.
::troll2::

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