TheSamba.com :: View topic - Massive Stumble (hopefully not from the 009)

Tue Sep 17, 2019 2:48 pm

Hey guys, I'm here to hear your thoughts on what's happening with my beetle. It's a 71 super, 1600 dual port, non-autostick, EMPI PICT 34-3, generator, points based ignition, 009 distributor.

What's happening: Massive stumble/hesitation/bog when I upshift from first to second gear. If I upshift at very high revs, it can sometimes power through the stumble but very rarely. The entire beetle lurches until I feather the throttle enough to keep it from stalling and get back into first gear.

What I've done: adjusted valves, replaced plugs and wires, new points, gap, rotor and condensor, new coil, fuel pressure is good. Fuel filter under tank up front. Adjusted carburetor per Benteley book, maxxed out the accelerator pump adjustment, confirmed it is squirting fuel. No vacuum leaks that I can find. Set timing at 3500 revs have 30 degrees advance, about 7 degrees at idle. Distributor doesn't begin advancing until around 1500 revs. I have oiled the wick.

I am at my wits end. After all of that work, the stumble on upshift/acceleration is still the exact same. Is this a symptom of a clogged jet in the carburetor? Is this an ignition issue? I'll post a picture of my engine in the comments when I get home today- hopefully you guys have insights that might help me.

Tue Sep 17, 2019 3:16 pm

You have the wrong distributor.

Tim

Tue Sep 17, 2019 5:12 pm

If you want to confirm it is your carb+distributor combo... set your idle timing to 15BTDC and take her for spin. Does it respond better as you accelerate from a stop? This shows how your carb+engine is responding to more timing just off idle. This is normally supplied by the vacuum advance of the SVDA or DVDA distributor that came matched with the 34Pict carb. Without the spike in timing the ported vacuum advance provides the engine hesitates.
Other than this test, DO NOT drive around with 15BTDC idle timing. It is VERY dangerous if you were to load your engine at higher rpms. It would go into detonation. Return your idle timing to 7BTDC and start your search for a good SVDA distributor to match to your carb.

Tue Sep 17, 2019 7:55 pm

apostlo wrote: Hey guys, I'm here to hear your thoughts on what's happening with my beetle. It's a 71 super, 1600 dual port, non-autostick, EMPI PICT 34-3, generator, points based ignition, 009 distributor.

What's happening: Massive stumble/hesitation/bog when I upshift from first to second gear. If I upshift at very high revs, it can sometimes power through the stumble but very rarely. The entire beetle lurches until I feather the throttle enough to keep it from stalling and get back into first gear.

What I've done: adjusted valves, replaced plugs and wires, new points, gap, rotor and condensor, new coil, fuel pressure is good. Fuel filter under tank up front. Adjusted carburetor per Benteley book, maxxed out the accelerator pump adjustment, confirmed it is squirting fuel. No vacuum leaks that I can find. Set timing at 3500 revs have 30 degrees advance, about 7 degrees at idle. Distributor doesn't begin advancing until around 1500 revs. I have oiled the wick.

I am at my wits end. After all of that work, the stumble on upshift/acceleration is still the exact same. Is this a symptom of a clogged jet in the carburetor? Is this an ignition issue? I'll post a picture of my engine in the comments when I get home today- hopefully you guys have insights that might help me.

You have a couple things at play here. The EMPI carb is hit and miss in quality. Matching it to a mechanical only advance is the second problem.

A restored German 034 SDVA will cure your off idle hesitations. VW designed the 34-3 carb to either the SVDA or DVDA distributor. The vacuum canister senses engine load and advances the vacuum advance timing quickly which prevents the off idle flat spot or hesitation.

I sell both restored distributors if you need one. :wink:

Tue Sep 17, 2019 9:04 pm

With a 009 you just have to rev the engine up a bit in order to get it to go. Usually it takes a bit more in first gear. Switch gears at the top of the RPM. If you look at the speedometer there are marks on it to show you where you should change gears.

If you want to switch your distributor there are a few options. You can spend $125 and up for a good Bosch rebuilt distributor.

Tue Sep 17, 2019 9:30 pm

heimlich wrote: With a 009 you just have to rev the engine up a bit in order to get it to go. Usually it takes a bit more in first gear. Switch gears at the top of the RPM. If you look at the speedometer there are marks on it to show you where you should change gears.

If you want to switch your distributor there are a few options. You can spend $125 and up for a good Bosch rebuilt distributor.

If I rev it past the 1st gear shift tick by probably half an inch, it can "kinda" make up for the stumble when I upshift into second. However, about half the time it still stumbles. However, I could believe I have a really bad 009 because there is some surface rust under the rotor. Like I said, I have to rev it over 1500 before I see any advance with the timing light.

Tue Sep 17, 2019 9:32 pm

wcfvw69 wrote: apostlo wrote: Hey guys, I'm here to hear your thoughts on what's happening with my beetle. It's a 71 super, 1600 dual port, non-autostick, EMPI PICT 34-3, generator, points based ignition, 009 distributor.

What's happening: Massive stumble/hesitation/bog when I upshift from first to second gear. If I upshift at very high revs, it can sometimes power through the stumble but very rarely. The entire beetle lurches until I feather the throttle enough to keep it from stalling and get back into first gear.

What I've done: adjusted valves, replaced plugs and wires, new points, gap, rotor and condensor, new coil, fuel pressure is good. Fuel filter under tank up front. Adjusted carburetor per Benteley book, maxxed out the accelerator pump adjustment, confirmed it is squirting fuel. No vacuum leaks that I can find. Set timing at 3500 revs have 30 degrees advance, about 7 degrees at idle. Distributor doesn't begin advancing until around 1500 revs. I have oiled the wick.

I am at my wits end. After all of that work, the stumble on upshift/acceleration is still the exact same. Is this a symptom of a clogged jet in the carburetor? Is this an ignition issue? I'll post a picture of my engine in the comments when I get home today- hopefully you guys have insights that might help me.

You have a couple things at play here. The EMPI carb is hit and miss in quality. Matching it to a mechanical only advance is the second problem.

A restored German 034 SDVA will cure your off idle hesitations. VW designed the 34-3 carb to either the SVDA or DVDA distributor. The vacuum canister senses engine load and advances the vacuum advance timing quickly which prevents the off idle flat spot or hesitation.

I sell both restored distributors if you need one. :wink:
Tim Donahoe wrote: You have the wrong distributor.

Tim

Sounds like that's the consensus, thank you guys. I'll do some reading and shopping.

Tue Sep 17, 2019 10:12 pm

apostlo wrote: If I rev it past the 1st gear shift tick by probably half an inch, it can "kinda" make up for the stumble when I upshift into second. However, about half the time it still stumbles. However, I could believe I have a really bad 009 because there is some surface rust under the rotor. Like I said, I have to rev it over 1500 before I see any advance with the timing light.

The 009 has a very slow ramp up. Once it ramps up then it advances fine. That is what you are seeing.

If you want to go with a rebuilt German Bosch here's a good option with a NOS vacuum canister. With any purchase you make you will want to ask if the vacuum canister is genuine Bosch. https://www.thesamba.com/vw/classifieds/detail.php?id=2127097

You can also purchase rebuilt distributors with used vacuum canisters.

Wed Sep 18, 2019 5:56 am

While the 009 (or any mechanical only distributor) can cause a pretty terrible hesitation, it should not cause a stumble.

For the first year I owned my bug, I ran a Solex 34pict3 carb with a Bosch 019 (also mechanical only advance distributor) and it did have a hesitation during shifts, but I never had any stumble or need to feather the pedals to keep the car alive.

Your descriptions sound like more of a problem with the carb. Sounds like something is clogged up in there. The 009 just isn't helping the situation either.

Some really talk down at the EMPI carbs, some swear that with proper attention and work they can be excellent. It is up to you as to what you want to use on your car.

At the very least, you need to give a very thorough cleaning to the EMPI carb you have on the car now. As said above the best option is to get yourself a matching German Bosch distributor and German Solex carb combo.

Here's the thread that chart above comes from, which outlines the year specific distributor/carb combos which came stock from VW:
https://www.thesamba.com/vw/forum/viewtopic.php?t=185095

For your carb needs I would contact Tim:
https://www.thesamba.com/vw/forum/profile.php?mode=viewprofile&u=184457

Wed Sep 18, 2019 6:03 pm

The 009 does not have a slow "ramp up" at all. :roll: Most of its 22° of mechanical advance is all in below 3000 RPM. The 009 immediately starts to mechanically advance at 1000 RPM. If your idle is at 900 RPM, as soon as you open the throttle and the RPMS increase, you're getting mechanical advance.

Where the SVDA wins the war is you get both the mechanical and vacuum advance when you crack the throttle. This overcomes the hesitation or flat spot you're feeling with the large 34-3 carb.

The German Bosch 009's work with the 30 series carbs though I prefer the original SVA distributors. Where they work nicely is with dual carbs. They are really good distributors in the right application.

https://www.thesamba.com/vw/classifieds/detail.php?id=2241598

I sell the restored SVDA's in many variants. This is the 043905205 or better known as the "034". I now use original Bosch vacuum canisters.

Thu Sep 19, 2019 12:40 am

AlmostHeavenWV_VW wrote: While the 009 (or any mechanical only distributor) can cause a pretty terrible hesitation, it should not cause a stumble.

That is correct. Where the 009 can cause a problem is at low rpm cruising, but if you are winding it out between shifts, the 009 will be at full advance (if it is timed right). With the 009 any VW timing info is worthless. I have used them for over 30 years. They might not be the best, but they can definitely be made to work. When I setup an engine to work with a 009, or any other mechanical advance distributer, I cut 2 notches with a triangular file in the pulley. One is at 28 Degrees before TDC the other 32 degrees. I then put a little dab of white paint in the notches, so its easier to see them with a timing light.

I use just an old fashion timing light with no advancing tech. I don't even use a tach to set timing, but just rev the engine until the distributer quits advancing, and rotate the distributer until one of the marks line up. Then I take it for a drive. The reason why I have the 2 separate timing marks is that each engine is different. Some will ping if you go over 28 degrees, others can go to 32. This way I can find the happy zone for each engine.

So if you have timed your engine right, a 009 will not bog hesitate, or stumble at a high rpm speed shift. If it does, you have an air leak, carb problem, or possibly an ignition issue with the coil or condenser.

Thu Sep 19, 2019 8:36 am

wcfvw69 wrote: The 009 does not have a slow "ramp up" at all. :roll: Most of its 22° of mechanical advance is all in below 3000 RPM. The 009 immediately starts to mechanically advance at 1000 RPM. If your idle is at 900 RPM, as soon as you open the throttle and the RPMS increase, you're getting mechanical advance.

Where the SVDA wins the war is you get both the mechanical and vacuum advance when you crack the throttle. This overcomes the hesitation or flat spot you're feeling with the large 34-3 carb.
A good writeup overall, but maybe a little misleading on the latter point above, in my opinion.

When you first "crack the throttle" from idle, you are also often starting to let out the clutch, and thus increasing the load on the engine. You now have a "power battle" of sorts going on in the engine -- i.e. between the available increase in power (due to increased flow of fuel+air mixture, plus any advance in timing), vs. the required increase in power (to overcome the increased load on the engine). If your "available" power isn't increasing as fast as the "required" power, then your RPM's will decrease, and you'll get no mechanical/centrifugal advance from your distributor -- your engine will likely "bog down" or "stumble".

The vacuum advance feature in SVDA and DVDA distributors, however, will give you a big shot of advance (and thus extra available power) the moment you crack the throttle, helping to overcome the tendency of the engine to bog down or stumble when you first let out the clutch / increase the load. As the engine RPM's begin to climb, then the mechanical/centrifugal advance will begin to kick in and increase, giving you even more total ignition advance and power.

If you don't have any vacuum advance, then you may definitely need to rev up the engine a bit to get some help (extra power) from the mechanical/centrifugal advance, before starting to let out the clutch. Some other common work-arounds for this sort of issue include things like increasing the amount of fuel shot into the carburetor by the accelerator pump and/or increasing the size of the jets in the carburetor (richer mixture = more power), decreasing or eliminating the hole in the throttle plate (once again effectively enrichening the mixture), and etc.

Thu Sep 19, 2019 8:54 am

I’m in the camp of ditching the 009. I had one installed shortly after I bought my car because the vacuum can was dead on my 205t. I didn’t know any better. The car always ran like crap. Dead spots, not fun to drive. I had an old timer rebuild a 205t for me and wow, what a difference. Seriously. Then I sent my original 205t to him and it’s sitting in a box as a spare. I also have an extra vacuum can as a spare as well. Never go to a 009 again.

Thu Sep 19, 2019 3:56 pm

baldessariclan wrote: wcfvw69 wrote: The 009 does not have a slow "ramp up" at all. :roll: Most of its 22° of mechanical advance is all in below 3000 RPM. The 009 immediately starts to mechanically advance at 1000 RPM. If your idle is at 900 RPM, as soon as you open the throttle and the RPMS increase, you're getting mechanical advance.

Where the SVDA wins the war is you get both the mechanical and vacuum advance when you crack the throttle. This overcomes the hesitation or flat spot you're feeling with the large 34-3 carb.
A good writeup overall, but maybe a little misleading on the latter point above, in my opinion.

When you first "crack the throttle" from idle, you are also often starting to let out the clutch, and thus increasing the load on the engine. You now have a "power battle" of sorts going on in the engine -- i.e. between the available increase in power (due to increased flow of fuel+air mixture, plus any advance in timing), vs. the required increase in power (to overcome the increased load on the engine). If your "available" power isn't increasing as fast as the "required" power, then your RPM's will decrease, and you'll get no mechanical/centrifugal advance from your distributor -- your engine will likely "bog down" or "stumble".

The vacuum advance feature in SVDA and DVDA distributors, however, will give you a big shot of advance (and thus extra available power) the moment you crack the throttle, helping to overcome the tendency of the engine to bog down or stumble when you first let out the clutch / increase the load. As the engine RPM's begin to climb, then the mechanical/centrifugal advance will begin to kick in and increase, giving you even more total ignition advance and power.

If you don't have any vacuum advance, then you may definitely need to rev up the engine a bit to get some help (extra power) from the mechanical/centrifugal advance, before starting to let out the clutch. Some other common work-arounds for this sort of issue include things like increasing the amount of fuel shot into the carburetor by the accelerator pump and/or increasing the size of the jets in the carburetor (richer mixture = more power), decreasing or eliminating the hole in the throttle plate (once again effectively enrichening the mixture), and etc.

We both saying the same thing. :wink: I just didn't have time to expand on it as you did. Bottom line is when you crack the throttle, the ported vacuum kicks in and is pulling the vacuum advance canister which advances your timing. This increases the RPMs which raise the mechanical advance of the distributor. Clearly this is the advantage of the vacuum and mechanical advance distributor.

Fri Sep 20, 2019 7:17 am

wcfvw69 wrote: We both saying the same thing. :wink: I just didn't have time to expand on it as you did. Bottom line is when you crack the throttle, the ported vacuum kicks in and is pulling the vacuum advance canister which advances your timing. This increases the RPMs which raise the mechanical advance of the distributor. Clearly this is the advantage of the vacuum and mechanical advance distributor.
Understood, and I agree. Was just trying to point out that the perception of mechanical/centrifugal advance effect as "ramping up slowly" isn't completely unwarranted. That 800 to 1,200 or so RPM range is where the engine does a lot of its work in getting the car up and moving from a standstill (assuming "normal/everyday" driving techniques). And in that range, the mechanical/centrifugal advance isn't really doing much to help increase engine power and RPM's. Once past around 1,200 or so RPM's, then yes the centrifugal advance ramps up pretty quickly. But by then your car should already be rolling, and need for that little peak of power (i.e. to "get things moving") has already largely passed.

In stock form, these are pretty low HP cars/engines, so little changes in available power (or lack thereof) are fairly noticeable. More so than what we may have been used to from driving cars with larger V6 or V8 engines back in the day, anyway. So if one desires a "normal" driving experience out of a stock VW 1600 DP engine (i.e. sans revving the engine / burning out the clutch, setting carb to dump lots of extra fuel, and etc. -- to get going from a stop), then they really do need that vacuum advance system installed and working correctly, to help make things run smoothly.