Won't idle when warm (yes checked past posts)

[Dhmp1970]

Hi everyone,

I have what sounds like a common problem and have followed all the posts that I could find, and still have not resolved. I have a 71 beetle convertible with the 34 PICT carb and the 009 dizzy with pertronix electrical module. It will idle fine until the choke is fully open, then will stall and will not hold its idle. The bug ran great until about two months ago when this started happening, and before it started happening the idle was set fine, and I had previously done all the timing and valve clearances to spec.

Here is what I've done:
1. I have cleaned the idle and main jets with carb cleaner and compressed air.
2. I have checked for vacuum leaks using starter fluid method. Found two - the intake boots and the throttle arm shaft. These are now resolved - replaced the boots and have covered the shaft areas with a liquid gasket sealant.
3. Idle cut off works fine
4. New fuel filter
5. Verified all vacuum points are plugged

Around the time this started happening, I had just had the bug sanded and resprayed, so there was a lot of little particles in the engine bay from the sanding. I figured some of this material got lodged in the jets, but I've really cleaned them to no avail.

Also, around this time I removed the old rotted tar board, and it is now bare metal, with a few holes that I plan to patch up. Could this be related to the stalling, that the engine is not properly warming up? (though it still stalls when the car has been driven for 10-15 min).

Any other leads or ideas?

Thank you!

Doug

[bluebus86]

check for intake leaks, use an aerosol flammable spray such as carb cleaner on all the manifold joints, base of carb etc...if idle speed changes either up or down coincident with spary, you have a vacuum leak there
confirm timing and correct sparkplug wire order
rebuild carb seeing as it sounds like it was exposed to dirt from sanding, simply cleaning the jets is not enough if dirt got in the carb.
make sure fuel pump is delievering correct pressure
check float bowl fuel level
try removing one spark plug wire at a time when running to see if removal of any one does NOt effect engine operation, if so, that is a dead cylinder.

good luck bug on!
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[heimlich]

I've dealt with the same setup. There shouldn't be any problem to get it to idle.

As bluebus86 stated, you need to check a few things. Another thing to check is when you start it put your hand over the carb. If the car doesn't stop you have a leak somewhere. If you feel a lot of suction on your hand and it does stop you probable don't. Just to check, spray carb cleaner or some other aerosol on the following parts but before you do that grab a fire extinguisher first and have it ready at hand.

From the carb down:
Carb to the intake manifold
Boots connecting manifold. They are red, black, etc and have two clamps on each
Next to the heads where the spark plugs are

Check both sides.

Don't spray too much around as the aerosol can damage paint.

If the engine RPM goes up at all while you spray double and triple check. That will check your intake leaks.

Let us know the results.
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[Starbucket]

Make sure the manifold heating tube gets hot within a min. or two. If not it's clogged and your manifold is icing up and will stall when choke fully opens.

[airschooled]

Have you tried a preliminary "setting" of the carb adjustment screws on the left side? I've seen three cars this year that have experience sudden unwillingness to idle because the o-rings on those screws aren't fat enough, and the screws are moving with engine vibration. If you want to try a free, easy, reversible test, turn the small brass screw out two full turns once the car is warmed up. Count the turns so you can revert to before if needed! Do the same with the big brass screw if the small screw doesn't have any effect.

If you try it, let us know the results.

Count 'yer turns!
Robbie
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[Dhmp1970]

Thank you everyone, I really appreciate your suggestions. I had actually previous done the check for vacuum leaks from carb to manifold (what I called the "starter fluid" check) and found and resolved the leaks (at the boots and at the carb), but didn't solve the problem. No leaks now, and I just did put my hand over the carb and the bug immediate stopped, so I'm crossing off vacuum leak as the cause. I will do a thorough carb cleaning and will let you know if still unsolved (I'm about to leave on a trip but will do when back). Checked the idle adjustment screws and they are nice and tight. Heat risers get nice and warm - cleared them out previously. I will also consider replacing the air filter, may have gotten blocked up from the sanding dust. Thanks again, Doug

[ldj1002]

Unscrew the idle jet just little if idle is good, take it out and spray carb cleaner in it and in the carb where the jet came from. If it idles good, good. If it doesn't find something to use as a shim so when you screw the jet down it won't go in as far and will be tight where it idles good, or get a tiny drill that just fits in the jet hole waller it around to make the hole just a little bigger. I like using the shim best.

[i_luv_my_bus76]

I am having the same issue...if you find a solution please keep us updated

[Brewpedlar]

Following. Im having the same problem on my 69 vert I just bought. I will try these fixes. Anxious to hear if anyone finds a solution on their.

[David_nc_72std]