The Ford Barn

rivcokid · 01-12-2023, 05:28 PM

Ugh! I'm stumped. The car runs and idles fine, except when i remove my foot from the throttle to slow down, or when just slowing down, it sputters and dies more than half the time. It will start right back up again. I can overcome this by keeping the throttle advanced, but then I'm grinding gears.

I replaced the gasket to the carb, which cured a problem on my other car of getting too much air. I've cleaned the carb out and the fuel line. When I try to adjust the idle screw, when I turn it out, the engine will sputter, but I can turn it all the way in and no dying like it should. In fact, there seems to be no difference in the idle from fully in to mostly out. I pulled the idle screw out to take a look at it and it appears to be just fine - no marks, no curves, no misalignments that I can see.

The car idles fine standing still, and runs fine too.

I should note that this is a 31 town sedan, stock, with a Zenith carb.

Thanks (again) for your help!

Y-Blockhead · 01-12-2023, 05:43 PM

The way you describe the idle mixture screw adjustment, it sounds to me like it may be a little too lean. With the screw all the way in and the throttle closed, you are shutting off the air for the idle circuit.

By "keeping the throttle advanced", you are no longer on the idle circuit.

I would suggest checking the throttle shaft clearance. It could be sucking air in at the shaft even when the throttle plate is closed. This is an often overlooked source of a vacuum leak. I put a dab of EZ Turn Lube on my shafts when installing.

Oversize shafts and bushing are available.

Might also check the float level. may be too low.

Mulletwagon · 01-12-2023, 07:04 PM

Another possibility is a vacuum leak - maybe intake manifold/block interface or windshield wiper line (if equipped with a vacuum motor). Please share the fix when known.

wwirz · 01-13-2023, 07:51 AM

Open the GAV a bit. Start at 1/4 turn open.

ThosD · 01-13-2023, 11:55 AM

My vacuum wipers did not work properly so I plugged the intake manifold port for the vacuum line and my engine settled down and ran smoother. Too lean at idle with wiper line attached.

rivcokid · 01-13-2023, 12:21 PM

Sponsored Links (Register now to hide all advertisements)

Thanks all - after this next storm I'll go and see if I can find the leak. I will definitely post a solution if/when I find it! Thanks again

nkaminar · 01-13-2023, 08:11 PM

The fuel level in the carburetor may be too low.

jeepguy1948 · 01-13-2023, 11:14 PM

I had the same problem and i figured it out by letting the car coast to a stop without using the brakes. When I found that it did not die when I did that I thought maybe the fuel was sloshing to the front of the bowl starving the engine for fuel. Was I right? I can’t say I only know that when I raised the float level a bit the problem went away.

01-12-2023, 05:28 PM	#1
rivcokid Senior Member Join Date: Sep 2018 Location: Riverside, CA Posts: 174	Dies when slowing down Ugh! I'm stumped. The car runs and idles fine, except when i remove my foot from the throttle to slow down, or when just slowing down, it sputters and dies more than half the time. It will start right back up again. I can overcome this by keeping the throttle advanced, but then I'm grinding gears. I replaced the gasket to the carb, which cured a problem on my other car of getting too much air. I've cleaned the carb out and the fuel line. When I try to adjust the idle screw, when I turn it out, the engine will sputter, but I can turn it all the way in and no dying like it should. In fact, there seems to be no difference in the idle from fully in to mostly out. I pulled the idle screw out to take a look at it and it appears to be just fine - no marks, no curves, no misalignments that I can see. The car idles fine standing still, and runs fine too. I should note that this is a 31 town sedan, stock, with a Zenith carb. Thanks (again) for your help!

01-12-2023, 05:43 PM	#2
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 5,849	Re: Dies when slowing down The way you describe the idle mixture screw adjustment, it sounds to me like it may be a little too lean. With the screw all the way in and the throttle closed, you are shutting off the air for the idle circuit. By "keeping the throttle advanced", you are no longer on the idle circuit. I would suggest checking the throttle shaft clearance. It could be sucking air in at the shaft even when the throttle plate is closed. This is an often overlooked source of a vacuum leak. I put a dab of EZ Turn Lube on my shafts when installing. Oversize shafts and bushing are available. Might also check the float level. may be too low. Last edited by Y-Blockhead; 01-13-2023 at 08:33 PM. Reason: Correct spelling.

01-12-2023, 07:04 PM	#3
Mulletwagon Senior Member Join Date: Jan 2019 Location: Florida Panhandle Posts: 585	Re: Dies when slowing down Another possibility is a vacuum leak - maybe intake manifold/block interface or windshield wiper line (if equipped with a vacuum motor). Please share the fix when known. Last edited by Mulletwagon; 01-12-2023 at 10:04 PM.

01-13-2023, 07:51 AM	#4
wwirz Senior Member Join Date: May 2020 Location: Corning NY Posts: 244	Re: Dies when slowing down Open the GAV a bit. Start at 1/4 turn open.

01-13-2023, 11:55 AM	#5
ThosD Member Join Date: Sep 2016 Location: San Jose, CA Posts: 47	Re: Dies when slowing down My vacuum wipers did not work properly so I plugged the intake manifold port for the vacuum line and my engine settled down and ran smoother. Too lean at idle with wiper line attached.

01-13-2023, 12:21 PM	#6
rivcokid Senior Member Join Date: Sep 2018 Location: Riverside, CA Posts: 174	Re: Dies when slowing down Sponsored Links (Register now to hide all advertisements) Thanks all - after this next storm I'll go and see if I can find the leak. I will definitely post a solution if/when I find it! Thanks again

01-13-2023, 08:11 PM	#7
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,903	Re: Dies when slowing down The fuel level in the carburetor may be too low. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

01-13-2023, 11:14 PM	#8
jeepguy1948 Senior Member Join Date: Jan 2022 Posts: 723	Re: Dies when slowing down I had the same problem and i figured it out by letting the car coast to a stop without using the brakes. When I found that it did not die when I did that I thought maybe the fuel was sloshing to the front of the bowl starving the engine for fuel. Was I right? I can’t say I only know that when I raised the float level a bit the problem went away.