Sputtering VW Bug
Matthew P. Harris
You've described the ailments of a VW bug engine with a dead
choke. The reason it works OK whenit is warm is that the choke is
stuck open. Either re-build the choke, or convert to a manual choke.
I recomend the latter. It's cheaper.
ciao
Matt Harris
m20...@newton.mitre.org
Greg Merritt
>Ladies and gentlemen,
>
>Here's a problem I have with a 1973 VW Bug. Basically it refuses to
>accelerate properly; upon acceleration from a stop the engine (and the car)
>will pick up speed, pause, cough a bit, cause the driver to use bad language,
>and then pick up speed again. This happens mainly whilst the engine is warming
>up. That is, it doesn't do this when I first start it and for the first couple
>of minutes (while the choke is closed, I guess). Then it occurs for the next
>five or ten minutes. When the engine is fully warmed up the problem mostly
>goes away (but not entirely).
>
>I have, of course, checked the timing and dwell, as well as spark plug gap.
>-------------------------------------------------------------------------------
>Steve R. SREN...@EAGLE.WESLEYAN.EDU
I had similar problems with the stock 34-PICT3 on my '71 (with California
smog equipment). However, I believe that your car should have a 34-PICT4
that includes a diaphram that's hooked up to the throttle (like on mine).
This little diaphram works against your inputs at the accelerator pedal by
resisting sudden changes in throttle position in order to keep emissions
down. For example, if you suddenly take your foot off of the gas while
cruising on the highway, this gizmo will let the throttle remain open for
a few seconds. If this thing is out of adjustment, it can make your carb
behave really funny. You can disconnect the thing entirely, and be all the
better off for doing so. (I'm assuming, of course, that you didn't already
check this when you rebuilt the carb.)
I hope that this will help. If any of it is unclear, feel free to e-mail
me at gr...@plasma1.ssl.berkeley.edu.
NOTE: USING A FRIEND'S ACCOUNT!!! SHE WON'T APPRECIATE FINDING MY MAIL.
RESPOND ONLY TO gr...@plasma1.ssl.berkeley.edu. Thanks.
-Greg
Dave Walden
sren...@eagle.wesleyan.edu writes:
>
>Here's a problem I have with a 1973 VW Bug. Basically it refuses to
>accelerate properly; upon acceleration from a stop the engine (and the car)
>and then pick up speed again. This happens mainly whilst the engine is warming
>up. That is, it doesn't do this when I first start it and for the first couple
>of minutes (while the choke is closed, I guess). Then it occurs for the next
>five or ten minutes. When the engine is fully warmed up the problem mostly
>goes away (but not entirely).
>
>idle, idle mixture, and accelerator pump have all been adjusted according to
>the manual. The accelerator pump in particular injects gas as soon as you pull
>on the throttle, and it injects the proper quantity. The hesitation problem
>existed before the carb rebiuld too.
>
>This hesitation, by the way, does *not* show up if I quickly punch the
>accelerator. If the car is sitting still I can blip the throttle fine. But if
>I push the pedal slowly and steadily, the engine will pick up rpm, slow, almost
>stall, and then pick up again.
My '74 Fiat X1/9 had exactly this problem AFTER I had cleaned
and re-built the carburetor. Part of the problem was cotton fibers
collecting in the holes in the emulsion tube of the primary throat
main jet. The fibers were from the cotton swabs that I used to wipe
away particles of crud after soaking in the carb cleaner. I
thought I had been careful about that, but.... some got left behind.
They formed a loose wad in the emulsion tube and the gas wasn't
getting sufficiently foamed to allow low speed operation.
After removing the cotton wad, the engine still had an unsteady
idle, although it accelerated well at full throttle. I bit the
bullet and removed the carb again and soaked the parts again,
tilting and re-tilting them so cleaner would flow through all the
passages. Then, I did just as all the manuals say to do: I blew
out the passages with compressed air. (I used the pulsing air
from a Black & Decker "Air Station".) When I tried the car again,
magic! Smooth idle, even at 400 rpm, and smooth steady acceleration
from low rpm on up. Apparantly, some softened crud had remained in
the idle circuit, and it took a blow-out to really remove it.
Dave Walden
djwa...@isi.edu
david erickson
sren...@eagle.wesleyan.edu writes:
>Here's a problem I have with a 1973 VW Bug. Basically it refuses to
>accelerate properly; upon acceleration from a stop the engine (and the car)
>will pick up speed, pause, cough a bit,...
>and then pick up speed again. This happens mainly whilst the engine is warming
>up. That is, it doesn't do this when I first start it and for the first couple
>of minutes (while the choke is closed, I guess). Then it occurs for the next
>five or ten minutes. When the engine is fully warmed up the problem mostly
>goes away (but not entirely).
A couple of things you might check: watch the choke in action: does
it heat up and open properly when starting? Does it close fully after
sitting all night? Does the automatic idle cut-off work? Is it good
and tight (you should not be able to loosen it by hand)? Is the
accelerator pump aimed properly (it should just hit the crack where
the throttle plate begins to open)? Is the idle richness adjusting
screw tip damaged?
Also look at the ignition system: does the vacuum advance work (try
sucking on the line, and watch the breaker plate rotate). If you
have one of those automatic throttle positioners that is vacuum
operated, make sure it works properly, and that you have no vacuum
leaks.
Well, that was more than a couple of things :-). Good luck.
-Dave Erickson
Drew Rankin
This is a reposting due to incorrect information in the previous posting.
In article <39...@ucbvax.BERKELEY.EDU>, gr...@plasma1.ssl.berkeley.edu (Greg Merritt) writes:
> Sender:gr...@plasma1.ssl.berkeley.edu (Greg Merritt)
>
> In article <1990Oct30.0...@eagle.wesleyan.edu> sren...@eagle.wesleyan.edu writes:
>>Ladies and gentlemen,
>>
>>Here's a problem I have with a 1973 VW Bug. Basically it refuses to
>>accelerate properly; upon acceleration from a stop the engine (and the car)
>>will pick up speed, pause, cough a bit, cause the driver to use bad language,
>>and then pick up speed again. This happens mainly whilst the engine is warming
>>up. That is, it doesn't do this when I first start it and for the first couple
>>of minutes (while the choke is closed, I guess). Then it occurs for the next
>>five or ten minutes. When the engine is fully warmed up the problem mostly
>>goes away (but not entirely).
>>
>>I have, of course, checked the timing and dwell, as well as spark plug gap.
>>-------------------------------------------------------------------------------
>>Steve R. SREN...@EAGLE.WESLEYAN.EDU
This is a problem that is not uncommon to bugs and pre-'72 (with upright
engines) type II's:
The heat risers may be plugged and causing the fuel to condensate
in the middle of the intake manifold due to the lack of heat to keep the
mixture vaporized.
The causes of the problem are as follows:
1) The heat riser tube attached to the intake is plugged with carbon or
other foreign matter and not allowing exhaust gases to flow properly.
2) There has been modification to the heat riser, either disconnection or
an after market exhaust without provisions for the heat riser.
The only solution is to clean out the tube or hook it back up (which ever is
the case) and go back to the stock set up. Which is probably the best setup
for a VW.
>
> ... I believe that your car should have a 34-PICT4
> that includes a diaphram that's hooked up to the throttle ... .
> This little diaphram works against your inputs at the accelerator pedal by
> resisting sudden changes in throttle position in order to keep emissions
> down. ... You can disconnect the thing entirely, and be all the
> better off for doing so.
A word or two on VW's emssion control. bad, BAD, BAD!
The original equip. smog control that VW put on the upright engines wasted
several hp that the little engine needed to keep up with the rest of the cars
that were cruising at 65 to 75 mph. It is best to remove all of that stuff and
go for a stripped down look in the engine compartment. On my '71 Super and '73
Std. Beetle, I opted to remove any smog control that was present which meant
removing the EGR equiped manifold and using an older one. This gave back lost
power and allowed for better economy (20/29 mpg). Other than that the two
were completely stock cars.
Good luck with your problem and I hope this fixes it. :-)
--- Drew
--------------------------------------------------------------------------------
Andrew Rankin COSC...@jetson.uh.edu
University of Houston
Comp. Sci. Dept.
--------------------------------------------------------------------------------
mun...@iccgcc.decnet.ab.com
recently did I read that the vacuum advance on the bug distributor was
at fault. There was always the mid-throttle hesitation when acceleration.
My fix at that time was to simply stay out of that section of the throttle.
A book that I recently bouight on hopping up vw bug engines highly
recommended to install the Bosch 009 distributor that has no vacuum advance
to mess you up. Simply plug up the vacuum line for the advance and the Bosch
dist. will mechanically do it much better. You can find the Bosch distributor
in the J. C. Whitney catalog or one of the many bug parts catalogs out there.