All Small Six Low throttle fuel flow

[adobejoe]

My 200six is on the road but I have an issue with maintaining idle/fuel under rapid deceleration. It will idle okay but when I quickly release the pedal it very often stall. Could it be low idle jet/passage loosing fuel? Maybe a vacuum loss/drop? Or this dashpot?

Older autolite1100. No spark control valve! I am using electronic ignition. Runs well at speed and high rpm.
Andy

 

[TrickSix]

There was an adjustment procedure for that anti-stall dashpot in the shop manual for my old car. It's basically a little gasoline filled shock absorber for cars with automatic transmission to slow down the the last little bit of travel as the throttle closes, hopefully to prevent stalling. But your carb is an oddball 1100, with a manual choke and no SCV. I suppose it's similar though.

 

[adobejoe]

Thanks trick six. Adjusted and improvement for a bit. Then lost low idle again. Could be I just need additional filter on metal line to carb. Maybe old varnish or dirt in line blocking ports….not sure. Runs well at higher rpm

 

[Frank]

Usually sudden snapping the throttle shut is a rich condition, not lean. Just FYI

 

[alwill923]

Needs a dashpot!
Temporary fix up the idle speed.

 

[Frank]

Needs a dashpot!
Temporary fix up the idle speed.

thus leaning the mix with sufficient air. . One of my dislikes of EFI era cars- they have no decel. Quick closing of the throttle makes emissions, even with MPFI. . The IAV sees that that never happens.

 

[adobejoe]

Still having issues with loss of fuel on deceleration. Engine stalls. Changed diaphragm in dashpot and got worse. Going to pull carb and clean low idle ports and reassemble tomorrow. Frustrating. Works fine at high rpm, like 2,000+

 

[drag-200stang]

If the carb. throttle/butterfly shaft and housing is worn too much. It can cause problems. When you let up it can move to a spot that lets in too much air with no fuel.

 

[DON]

Refresh my memory: IAV??
If there is too much play in the throttle shaft, it is fairly easy to put bushings in. FYI
It would be interesting, lean out the idle mixture, maybe 1/4 turn and see if it makes any difference on the quick decel. You could also try to go richer 1/4 turn as well. If the idle quality will let you, go a little more

 

[Frank]

Still having issues with loss of fuel on deceleration. Engine stalls. Changed diaphragm in dashpot and got worse. Going to pull carb and clean low idle ports and reassemble tomorrow. Frustrating. Works fine at high rpm, like 2,000+

Still having issues with loss of fuel on deceleration. Engine stalls. Changed diaphragm in dashpot and got worse. Going to pull carb and clean low idle ports and reassemble tomorrow. Frustrating. Works fine at high rpm, like 2,000+

Are you sure it's loss of fuel. Flooding stall on decel is much more common.

 

[sixtseventwo4d]

Have you checked/adjusted the base ignition timing?
How well does your idle respond when turning the idle mixture screw?

 

[drag-200stang]

I have never done it, but I know that it is not uncommon to replace shaft and rebush a carb.
I agree with Frank, that it could be a too rich issue, maybe float to high.
Do not rule out electrical, grounds, ignition switch etc.