Hi:
I have a stock '69 428CJ R-code Mustang. Having difficulty keeping her running at engine speeds below 1500RPM. When I back off on the throttle to anything less than about 1500RPM she dies as if I shut the key/ignition off. No sputter, just flat out quits. I've been told it may be a vacuum leak, but I don't hear one and I would think that a vacuum leak severe enough to make her quit as quickly as she does would be somewhat audible? For example, when she was running well I could disconnect the vacuum line to the shaker hood and she would noticeably shutter and shake and you could definitely hear the leak but she would still run, albeit rough. Now she just flat out quits at anything approaching an idle.

Anyone have similar experience's they might share? Any idea where I might look?

Thanks for any help!

 

where are you located?

 

When was the last time it ran right?

If the idle circuit in the carb is totally offline it would probably die directly as it came off booster / transition slot fuel supply

Has it sat for years or was it boss pimp last week and now just wont idle?

 

Hi barnett468: I am in California

 

Hi Gun Jam: She sits a lot. It probably sat for a few months when she started behaving like she is now.

 

Does it have a choke plate? Try forcing it closed even when warm and see if you can get the idle to come down lower. It should be closed enough that you can get a pencil between the plate and horn. This will cause an artificial increase in vac over the boosters and allow them dump fuel at lower rpm.

You might try removing the idle mix screws and cleaning out the passages with carb cleaner. Turn the screws in until they seat (count how many turns) then removed them. then reinstall until they seat then back out by that turn count.

-Gun