Ive tried everything to fix acceleration stumble.....

[21golden007]

Its had the same problem since i bought it a couple months ago. Idles fine, revs up fine when in neutral even if i hammer on the gas, but when i go to take off at low rpm from any gear, it stumbles to the point of almost dying and i have to really work through it. Isn't it odd how it only does it under load and not in neutral?

ive tried the below-

3 different carb setups- stock, single HPMX off another bug, and Dual hpmx's. it has the same problem with all of them even after trying different carb adjustments and accelerator pump adjustments

a bosch 009 distributor and a pertronix 009 style with electronic ignition. no difference.

a bosch ignition coil and flamethrower ignition coil, no difference,

multiple timing setups from 5 btdc to 15 btdc at idle. no difference

adjusted valves, no difference

tested for carb air leaks using spray test and cover inlet up test, no problem there

checked fuel pressure. Its around 3 psi for duals, no problem there

shored up any exhaust leaks

replaced spark plugs and wires

I finally checked compression probably later than i should have and every cylinder is right around 100, which seems low. Would this cause a stalling out/hesitation problem under load? I wouldn't think so but I am at a loss. I feel like I've tried everything.

[Lingwendil]

Were the distributors both electronic, or were you able to try with points?
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Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

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[21golden007]

[VW_Jimbo]

The 009 is known for a large flat spot at acceleration. Get a vacuum assisted advance distributor. You also would benefit from weight advancing to. I have a clone 034 distributor with electronic ignition. I love it! It Has worked great back when I was running a 30PICT-something, and then again with the dual 44 Webers!
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[AlmostHeavenWV_VW]

Agree with the above which Jimbo said. The 009 is likely a large contributor(if not the entire) to the stumbling off acceleration from a stop.

I had a mechanical-advance-only distributor on my beetle when I bought it. Got a proper distributor with mechanical and vacuum advance and the car pulls strong from a stop, even on the hills.

I personally have a restored Bosch distributor, but many (Jimbo included) have good luck with the SVDA 034 clones. Your choice

Restored distributors available from these guys:
Both these guys do lovely work:
Bill (wcfvw69)
https://www.thesamba.com/vw/classifieds/search.php?username=wcfvw69

Glenn
https://www.thesamba.com/vw/classifieds/search.php?username=Glenn

Or the new 034 clones are available pretty much everywhere. Usually the pertronix brand is what you'll find.

Also, you have to match your carb to your distributor for best performance in these little engines.Check out the charts in Andy's thread here for info on matching it up:
https://www.thesamba.com/vw/forum/viewtopic.php?t=185095
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1973 Standard Beetle
1600DP AK case
Solex 34PICT3 Carb
Bosch DVDA 205AJ Distributor

[Chadabear]

https://www.thesamba.com/vw/forum/viewtopic.php?t=340069&highlight=dvda

[21golden007]

[21golden007]

Also, Wouldn't the 009 hesitation/flat spot be occurring in neutral as well when hammering on the gas? My issue only happens when moving coming out of low RPM.

[Q-Dog]

You do not static time an 009. Set the 009 timing to 32° btdc with a strobe timing light. Ignore where it lands at idle. If it pings under load, retard the timing a degree or two.
_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[rayjay]

If you have tried 15* btdc initial I think you have eliminated the ign timing as the problem. Usually a flat spot off idle is due to inadequate pump shot whether it's a late delivery of the pump shot or just not enough pump shot due to too small pump shooter orifices. The load doesn't last long when hitting the throttle in neutral so the motor can catch up easy as to compared with pulling off from low rpm.

I would do a leakdown test next. See if you have lots of blowby or leaky valves. These play havoc with transitions. I would also check valve lift in today's world of junk parts.

[rayjay]

[joemama]

I think its important to know what carburetor you currently have on the motor. Also, 009 distributors are timed by total advance, 30 to 32, no more than 32. Have you checked that the distributor is in fact advancing? Checked for vaccuum leaks, check the accelerator pump?

[ashman40]

Found a nice thread that compares the advance curves of different distributors:
https://www.thesamba.com/vw/forum/viewtopic.php?t=640208

Here are two pics from that thread to compare the curve of a 009 (single spring) and the 034 SVDA distributor.
Find the 009 line (gold) in this pic:

Compare to this 034 (SVDA) curve:

Both distributors are initially timed at 7BTDC. Below are the realized ignition timing at different rpms...

At 1000rpm:
009 = 10BTDC
034 = 7BTDC

At 1250rpm:
009 = 11BTDC
034 = 17BTDC (7deg + 2deg mechanical + 8deg vacuum)

At 1500rpm:
009 = 12BTDC
034 = 29BTDC (7deg + 4deg mechanical + 18deg vacuum)

At 2000rpm:
009 = 18BTDC
034 = 35.5BTDC (7deg + 7deg mechanical + 21.5deg vacuum)

You can see that once you get to more than 1000rpm the SVDA distributor is quickly increasing the ignition timing much faster than the mechanical-only 009. This increased ignition timing appears as more "seat of pants" power from the engine (all else being equal). The 009 curve is basically a straight line that increases as rpms increase. This means at speeds just off idle there is very little additional ignition timing. But look at the way the vacuum advance line spikes just as the throttle is opened from idle/closed position. This ignition timing spike counters the bog you feel with the 009.

If you have a stock 34Pict-3 carb, marry it with an SVDA distributor and you should see good acceleration from a stop.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[21golden007]

I appreciate the slew of responses. I think next step is picking up a timing light from NAPA this afternoon.

Joemamma, I currently have the dual 40 HPMX's on which I know is not ideal as the setup is probably hardest to tune out of them all, but thats what I would like to stick with going forward. Ive done best lean idle procedure and synchronized them. The fact that the same problem seems to persist with 3 different carb setups makes me think its not the issue but ive been throwing my hands up in the air for two weeks now so... I will say that even though the issues exists among the three carb setups, the stock carb ran the worst out of them all (maybe due to lack of vacuume advance?). At times it would refuse to accelerate at all, just sputter sputter sputter. With the HPMX (single and dual setups) it'll at least take off at slow acceleration.

I do understand from research that the SVDA is the way to go, but I also know 009 is so common that the level of studder/hesitiaton/flatspot that i have just cant be normal 009 or not...

[mukluk]

This is a very common issue with dual port enginges equipped with the 009 distributor. You have two choices on how to address the low rpm stumble problem: either replace the distributor with one that has a vacuum advance, or install larger idle jets. Be aware that while the larger idle jets will fix the stumbling problem, they'll also increase your fuel consumption.
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1960 Ragtop w/Semaphores "Inga"

[vwracerdave]

I'm just shaking my head. All this advise without knowing anything about engine size or details.

Your problem may be because your heads are too big, maybe your cam is too big, or maybe your exhaust is too big or maybe all 3.

Give us as many details about the engine you can.
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[ashman40]

[frenchroast]

I have a stock SP 1585 that had a bad off idle flat spot. Increasing the main jet size fixed it. The stumble is there with either an 009 or a 205T SVA distributor. It’s also there with either an H30/31 or 30 PICT 2 carburetor. It was “less bad” with the SVA but still not acceptable. The only thing in my case that cured it is increasing the main jet to a 130. I’m at sea level with 10% ethanol on a bone stock motor (except it’s now a 1600 not a 1500). I static time at ~3deg BTDC. I also need a top end rebuild (low compression, blow by).

[21golden007]

[mukluk]