dying upon deceleration or stopping at a stop sign

[mebco09]

I'm sure this is an easy fix, but I can seem to figure it out.

77, all stock 302, automatic. When coming up to a stop, nearly every time it will stall. Turn the key, starts right up. Only happens when it is warm, on regular idle (not high idle). Took it through a graduation parade and had to keep it in "N" every time we stopped to keep it from dying.

Anybody have any thoughts at what to check first?

I've adjusted the idle speed, doesn't seem to do anything. Started doing this out of the blue after sitting for 2 months or so. (ethanol gas). Sprayed carb with cleaner. No help.

Wondering if the fuel pump is weak.

 

[75MIKE]

Fuel filter would be the very first thing I would check.

 

[Seventee]

Fuel pump or filter would be more of a problem while you are driving. Chances are either your choke is sticking or the idle circuit is clogged. Check to be sure your choke is fully open when warm and you can try turning your idle mixture screws out a bit, like 1/4 turn or so to see if it makes any difference. Could also be a vacuum leak somewhere.

 

[ugly74]

Wouldn’t hurt to check your float level

 

[blubuckaroo]

Fuel deposits can clog the teenie idle air bleeds, which will make for a bad idle and make idle mixture adjustment impossible.
I like to remove the air bleed screws and use aerosol Chemtool, with a long tube, to flush out the port. No need to remove the carb for this. Just let the Chemtool run down the venturi.

Also, on a '77 you should have an idle solenoid. If it's functional, that's where you need to make your idle speed adjustment.

 

[Rustytruck]

if you still have your factory emissions package check your egr Valve for excessive carbon deposits. a lazy or stuck valve in the egr can cause these issues.

 

[blubuckaroo]

if you still have your factory emissions package check your egr Valve for excessive carbon deposits. a lazy or stuck valve in the egr can cause these issues.

Good job!
I forgot that one.

 

[73azbronco]

Leaky line to c4 modulator. Whats you vacuum do during this?

 

[mebco09]

Thanks guys. Ill tear into it this Saturday and see if I can get it to behave.

 

[Jebus]

Does it have vacuum power brakes?

Would not hurt to check the PCV valve and hose connections too...