Stalls Coming To A Stop (Intermittent)

[Grug]

1600, DP, 009 distributor, 34 PICT 3

Lately, the motor will intermittently die when you come to a stop when the clutch is engaged (you can pop the clutch and bring it back to life). If it does stall, it will start right back up, no problem. It runs on the road fine and it will sit and idle all day in the driveway (although I'll admit it's a bit of a rough idle).

I do think I have manifold icing issues as the neck of the intake manifold and the heat risers are relatively cool to the touch. Just wondering if plugged heat risers could create this intermittent issue.

I checked for intake leaks with WD-40, but didn't find any.

I did a search and a number of people experience a stall at stop signs, but it seems to be when they're pulling away. With me, it's the opposite.
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"If you're going through hell, keep going."
Winston Churchill

[torontojamme]

I was having similar problems, though I honestly didn't think of popping the clutch to bring it back, seems obvious now! Once I cleaned out my idle jets the problem went away.

[Beeble1]

X2 on the idle jets.
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Beeble1, 1973 Super (o\_|_/o) 1600cc w/ Dealer A/C
Beeble2, 2013 Beetle 2.5L Daily Driver

Dealership items from Bishop-Wayne Volkswagen & Turner Volkswagen in Kankakee, IL wanted

[ashman40]

Can you provide more detail about WHEN the stalling occurs? Is it linked to the engine rpms going from high to low? Or it it linked to inertia?

For example try these tests:

Driving at constant freeway speeds... press in the clutch and let the rpms drop to idle w/o pressing on the brake. This will drop the rpms w/o deceleration. If there is a problem with too much fuel being forced at high rpms into the carb it will show up with the engine stalling/dying. After the engine dies apply brakes and pull over. Remove the top of the carb to see if the fuel level in the fuel bowl is too high, indicating too much fuel pressure.

If the above doesn't cause the engine to stall, gently apply the brakes to slowly decelerate to a stop. Does this slow stop prevent the idling engine from stalling?

If the engine does not stall, run the same test but this time after you drop rpms to idle while at speed step on the brake hard to force fuel to slosh around in the fuel bowl.

You are trying to understand if the problem is from too much fuel in the fuel bowl, or if it is a tune problem where the engine doesn't like running at high rpms and then dropping to idle. Some models of Pict carbs came with a dashpot-type device to prevent the carb throttle from slamming shut.
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AshMan40
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'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!}

[VW_Jimbo]

Time for a rebuild. Crankshaft endplay issue.
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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!

[scrivyscriv]

A rough idle and the engine dies coasting with the clutch pushed in..
Blow out the idle pilot jet and its bore, and make sure your choke is adjusted with the engine cold. I know you said you checked for vacuum leaks, but it really takes some experience to find them with aerosols. You can make a DIY smoke machine for pretty cheap.
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Robert in Memphis
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.

[ashman40]

One previous problem someone had was the intake was so loose that it pivoted forward on deceleration and the choke terminal (this was on a Weber 32/36) made contact with the fan shroud and shorted the ignition coil so the spark plugs stopped firing. But every time he went back to check it the intake had fallen back in place and looked normal. The same movement on a Solex PICT carb is usually not possible because the heat riser tubes hold the intake firmly in place. But if you cut off the tubes as some do... it might be possible.
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AshMan40
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'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!}

[Tim Donahoe]

It might be as simple as not having your rpm’s up high enough. Try 900 rpm’s.

I had an intermittent issue like this when I first got my carburetor back from Volkzbitz. Tim asked me what my rpm’s were, and I told him between 800 and 850. He told me to get closer to 900. That did the trick. Over four years now and no carburetor issues whatsoever.

Tim
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Let's do the Time Warp again!

Richard O'Brien

[Grug]

Thanks for the prompt replies, folks.

I think I'll start with cleaning out the idle jet (I believe that's the 'pilot jet' on the right side of the carb...right?). Although I've removed a carburetor before, I've never actually had one torn apart.

I did try adjusting the bypass screw and volume control screw (the two screws on left side) in an attempt to get a handle on the idling issue. And as I said earlier, it will idle all day sitting in the driveway (albeit it roughly). The stalling is a road issue. With a tach / dwell attached, the idling will fluctuate between 800 and 1000 (give or take). Prior to my adjustments, it was sitting closer to 1200.

If the pilot jet cleaning makes no difference, I will try the road test regarding inertia versus decreasing RPM's. I'll be honest, I'm a little nervous about pulling the top off the carburetor out on the road; seems so much 'safer' within the confines of my garage

I'll update my progress. Will also try and upload an image (see if there's anything obvious I'm missing).
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"If you're going through hell, keep going."
Winston Churchill

[Frodge]

I keep my idle above 900. Always have. Probably closer to 925-950. Why would you want the engine loafing after a hot highway run and you pull up to a red light etc.....

[Grug]

Here's the carb. Note the bent accelerator pump gear (must've been done by the previous owner to accommodate the alternator). Also, note the electromagnetic shut off is missing (but the port is plugged). And of course there are other plugged ports as I'm running the 009 distributor.

Despite these 'alterations' the carb. was working up until a short time ago. The idle was always a little rough, but the stalling at stop signs is new.

I know it's kinda' dirty. Cleaning it up is on my list of things to do when I put the Bug to sleep for the winter months.

_________________
"If you're going through hell, keep going."
Winston Churchill

[Frodge]

You could have a vacuum leak where the accelerator linkage is, if it were bent. Possibly has gotten worse since you started using it.

[Grug]

[Q-Dog]

WD-40 may not be the correct diagnostic tool. I believe they got rid of the flammable propellant some years ago.
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Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[ashman40]

[Grug]

First Update. I wanna' try some of the other solutions offered, but for now...

So I removed the carb. I pulled the top off and took a few things apart and cleaned them (I circled them in the diagram). When I put it all back together it didn't seem a whole lot better; maybe slightly. One thing I did note when setting the idle again was that the bypass screw seems incredibly sensitive. I swear I saw a change in RPM's by just pushing on it with the screwdriver (as opposed to turning it in or out). I didn't fully remove the bypass screw when I had the carb off the car. Looking back, I should have

Upon reviewing my carb diagram, it looks like there's a rubber o-ring on the bypass screw. Is that correct? If that o-ring was wonky, could that give me my erratic idle and stop sign stall?

And finally, I road tested it and although the idle did drop a lot as I engaged the clutch and came to a stop...it didn't stall (it sounded like it was gonna' though).

How about that corrosion on the lower butterfly valve? That can't be good.

Almost forgot. I'm not sure when the carb was last rebuilt. The previous owner had no idea. I think it would be safe to say a looooong time.

_________________
"If you're going through hell, keep going."
Winston Churchill

[ashman40]

[Grug]

I drove the car twice since the last post. The first run wasn't too bad and I experienced only one stall (although that's one too many). The second run was really bad It stalled more than it ran as I approached stop signs. As soon as the clutch is engaged, you can tell the engine wants to die as the idling drops like crazy.

Anyway, I pulled the carb and removed various pieces for cleaning. I used compressed air, but I didn't use carb cleaner...yet. I need to pick some up, soak, and apply air again.

I did notice what looks like a tiny slice in the volume control screw o-ring (if you look closely, you can just see it in the image below). But I thought it was the pilot jet that was the Holy Grail of idling

I also did the fuel bowl level test and as you can see in the image, the level looks ok. It's between 5/8" - 3/4" from the top. I also directly sprayed WD-40 on the EGR plug, throttle shaft, and again on the various jet locations.

Finally, I felt for any obvious play in the throttle shaft and it seems nice and tight. I couldn't feel any, in fact

So for now the plan is to get some carb cleaner, do a thorough cleaning and give it another try. I don't have a rebuild kit or I'd replace that volume control screw gasket. (A rebuild kit is about a week away; if I go that route.)

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"If you're going through hell, keep going."
Winston Churchill

[Dark Earth]

Here's a popular diagram showing the inner workings.

I think you found your problem. Those little o-rings cause so much grief.
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My Build: '69 Baja - Dark Earth Version

~I'm almost done. I just lack finishing up.~

[Grug]

That 'slice' look like it might be enough to give me idling grief? It's not all the way through the ring, but I did easily notice it upon close examination.

It's interesting that the diagram you included lists the 'Idle Air Mixture Regulating Screw'. I've been calling it the 'Volume Control Screw' as I thought it had very little to do with idling
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"If you're going through hell, keep going."
Winston Churchill