Engine shakes excessively at idle

[Donewright]

Greetings,

This is my second post related to my new to me 1969 VW Dune Buggy.

Engine:
H 5692428
88 Kit - Stroke 76mm
Carburetor - 34PIC T-3
Dual Port
Mechanical Advance Distributor (Points replaced with electronic module)
External Oil Filter
Bosch Blue Ignition Coil

Observation: The engine starts up instantly hot or cold. The engine is smooth while the automatic choke is on. When the choke releases, the engine starts bouncing back and forth (excessively). The engine will eventually shut off after a couple of minutes if I do not bump the throttle. I did turn the idle screw one turn and it will now continue to idle without throttle input.

I have completed the following:
- Replaced the plugs with NGK D6EA gapped to 27
- Replace wires
- Adjusted the Valves to .006 gap
- Oil/Filter change
- Transaxle Oil Change
- Checked and Cleaned the Idle Jet in the carb (Marked 55)
- Increased the Idle speed from 790 to 890~ish per my timing light/tachometer
- Visually checked the three Transaxle mounts - They look intact

I have attempted to check timing. When at idle i can't get a smooth reading, the numbers on the pulley just seem to bounce all over and it is impossible to get a single number to read.

When I adjust the digital advance on the timing light, I get TDC aligned with the case split when I reach 28 degrees. That reading is stable and can easily be read with the strobe light.

So I guess whatever is causing my engine to shake like a Hooters Waitress at idle is also affecting my ability to read the timing at idle ?

Note: The engine is super smooth above idle speed.


Any advice is greatly appreciated.

[tasb]

I suspect you have carburetor issues. There are actually three adjustment points on a 34 PITC 3. See


rob and Dave’s VW pages.


Your carburetor and distributor are not the best match as it looks like you have a ubiquitous 009- uh oh 9 distributor.
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[my3bugs]

when ya rebuild these 34 pict 3 carbs , the initial setting is 2 1/2 turns out for both screws , it usually starts there but needs fine tuning after a warm up .....

[my3bugs]

its hard to see it good in your pic but your carb looks to be modified a bit , looks to have the second throttle arm removed as your not using any smog equipment here ..... so not as many adjustments as a bone stock one .


you dont have any heat riser from the manifold to the headers conected , is it cut off or what ?

so just make sure the headers arent drilled thru there or youd have exhaust leaks .

do you have another blue cap on the driver side of the carb port plugged off ?

[Donewright]

Thank you,

I will check Rob and Dave's page.

I have read that the 009 mechanical distributor does not always play well with these 34PIC T-3 I just don't recall seeing what the symptoms of that incompatibility are.

I am attaching close up pics of the carb

[my3bugs]

with the 09 its kinda hard to get it to idle good , might run good but back at idle not so much for me . i have ran an 09 for years and you can get it to work . BUT i finally broke down and got a 034 distributor and it idles so much better .


i dont know anything about em but i see new cheap Chinese 034 distributors lately . prolly junk but just read the add to see what it says about the 09

https://www.jbugs.com/vw-distributor-svda-style-va...OIQAvD_BwE

[Donewright]

I would be happy if the solution was to just replace the distributor with this one form jbugs: https://www.jbugs.com/product/186504.html

But can I prove that this incompatibility causes the engine to shake? Is the shake just the result of the spark and carb out of sync with each other at idle?

I don't mind spending the money to make it idle correctly:)

[my3bugs]

you clearly have tune up issues , we cant see what it is .......you can prolly make it work with what you have , set your points , timing , and adjust your carb . when it runs can you get a timing light on it to see where its set ? cant adjust the carb till the electronics are SET !!!


you have some electronic module so maybe the points are good , check timing , then adjust carb .

[my3bugs]

in your second pic what is the rod thing sticking out between your pump n carb , that doesnt look stock to me ??? looks to have some lettering ???


looks like it says REMOVE ???

[Donewright]

yeah, I'm stuck on setting the timing at idle. With the timing light on the marks, the marks are literally jumping all over the place at idle. When I hit the throttle, the marks stabilize at 28 degrees.

So, I'm back to trying to determine why the engine has such a shake at idle and the timing marks are jumping all around at idle.

[DesertSasquatchXploration]

https://www.jbugs.com/vw-distributor-svda-style-va...OIQAvD_BwE

I bet my left nut those have a sloppy bushing so the point gap is all over the place wont run worth $hit. J bugs is just off-loading JUNK. Everything they sell is JUNK.

[my3bugs]

did it work before distributor module ? i like my points you cant look at that module n see if its opening or anything , its now a mystery electronic part in your distributor ..........i like to keep it simple .

[Donewright]

my3bugs,

It seems to be a rubber cap. covering a tube that goes into the intake manifold

Funny that it says remove.

I have no contact with the man that built the engine, so I'm trying to figure this all out

The distributor module was already installed when I got it. I do know that the idle did not get better or worse after the work I have performed.

If going back to points would solve my idle issue, I have no problem with that either.

What brand of distributor does everyone recommend ?

[my3bugs]

myself id prolly put the points back in n see how it runs . i think its just points n a rotor needed to go back to stock .

i think you said when you gas it the timing looks to be 28 degrees ? should be closer to 30 with this dizzy fully advanced . but i dont think thats your problem , just scratchin my head .

when ever running the modern electronics you/i want a set of points n a rotor in the trunk just for in case . if thats not it you can put your electrinics back in .

i had one of those at a time , dont know exactly what i did but i touched the wire to the coil wrong side and it was toast that fast , points wont do that so i stay with points .

it was like a 100 dollar goof !!!

[my3bugs]

myself i like back up plans , when i replaced my 09 with the 034 i undid the distributor clamp nut n removed it as 1 unit clamp n all , now its already perfectly timed n ready to drop back in - in minutes , just find TDC and drop it in n tighten it . ok you gota push in the plug wires takes another minute .

i have it marked as an 09 # 1 isnt in the same place as 034 #1 .

another thing i do is when ya finally get it running right i put a small dot of model paint between the distributor and the clamp so if it ever moves i can see where it belongs that easy .

i have the 09 in my daily bug tool box as a back up . my trunk tool box is kinda big these days .....

[SBD]

I know this seems stupid, but just to be absolutely sure... check that your plug wires are on in the correct order. Sometimes it's the simple stuff. A couple of switched wires could maybe cause your problem?
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[mukluk]

So the engine idles fine with the choke on, then idles unevenly and will eventually die with the choke off. Seems pretty clear to me the problem is your idle mixture is too lean. You're looking at either incorrect carb adjustment/setup, dirty passages/jets, or a vacuum leak.
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[scrivyscriv]

just a casual observation but it doesn't really matter what your timing is reading at idle with a mechanical advance distributor. You could be describing timing scatter, carburetor not tuned or dirty, ignition misfires... could be anything causing the shaking.

Ignition is electronic so nothing to adjust there, but do make sure your + and - wires are on the correct coil posts. John @ AC.net advises that most "carburetor problems" people have are actually ignition related.

Set timing to 28ish degrees total advance, disregard the idle reading
It sounds like you may have some FOD in an idle circuit. I'd highly recommend tearing the carburetor down and doing a good ultrasonic cleaning. To my understanding, all the fuel going into the idle circuit first passes through the main jet. You need to make sure there is no sediment in the bowl and that the main jet is clean/not varnished. At a minimum, set the idle mixture and speed to spec - IIRC 950 rpm.

While you're in there, check for intake and exhaust leaks.
And, worst case, maybe you have some sloppy internal engine clearances or balancing problems.
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Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

[Donewright]

Thank you for the replies.

I already saw 28 degrees of advance when using my timing light and increasing the throttle by hand.

I'll skip the step to set/verify the idle advance.

Next, I'll walk through the steps to set the idle mixture and idle speed screws on the carburetor (Making note of currently how many turns out they are) .

[oprn]

I have never been able to get a consistent carb tune on an engine with a stock intake with no heat riser. They run ok... sort of... but not really... one day and worse the next.

Any idea What cam is in that engine? The dual cannon exhaust is not helping the idle and low end either. I suspect it's a combination of cam, exhaust, distributor, and lack of intake heat that is adding up to prevent it from running right and all 4 need to be addressed.

What you have there is another one of thousands of old VWs that the owners/builders have made poor choices on. There are at least 4 other things that I would change on that Buggy too based on that one photo.
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