1965 Mustang Stumbles after deceleration

daw00l · 06-25-2009

I have a '65 mustang with a C code 289 and a 4 speed toploader that stumbles after I take my foot off the gas pedal. It has a Carter AFB 4 barrel on it with EGR that is not hooked up. I just rebuilt the carb and still does it. I have also checked my vacuum hose and plugged it at the source and that made no difference. The car idles fine, and runs fine other than that. If I take it off and put my foot back on before the car regains its normal idle, it usually dies. Does anybody know what would cause this? Could it be that I am not using the EGR? I would think that it would need a dashpot but the fords with manual transmissions did not have those.

Thanks

rocky289 · 06-25-2009

Explain how this problem shows if you are driving on the road.
For example cruise at 50 & alternate the throttle.

daw00l · 06-26-2009

it doesnt show at high speeds, but if i were to come to a stoplight, or slow down to about 5 mph, the engine would stumble and then regain itself. I could also be driving along, put it in nuetral to coast, let off the gas, and it would do the same thing. Any time that it is in nuetral and I let my foot off, it does this.

rocky289 · 06-26-2009

Did this fault come on gradually or after some work was done on the car?
This EGR, is it on the carb or manifold?

daw00l · 06-26-2009

I think that it had started after I rebuilt my transmission, and I remember it getting gradually worse. The EGR is on the carb.

rocky289 · 06-26-2009

Sorry I'm not familiar with one of those.
Maybe the Greek might have a sugestion.

daw00l · 06-27-2009

Ok well thanks anyways

429ragtop · 07-02-2009

hook a vacuum gauge up to the manifold. Snap you throttle quickly to wot and release. Should read close to 25 on release before it settles back to normal. Sounds like a possible vacuum leak.

PaulS · 07-02-2009

You need to adjust the carb - and perhaps richen it because the carb is set for use with the EGR. You don't want to run an EGR valve on an early mustang. Remove and block the EGR and its passages and richen the carb mixture the equivalent of 1 or 2 jet sizes. (sorry, Holley Back-ground)

The Greek · 07-02-2009

If what PaulS states doesn't work, still keep that EGR system blocked off and try a dashpot. When the throttle plates quickly close, there's a momentary lean condition in the intake manifold. Installing the dashpot will slow the closing of the throttle plates.