PLEASE lend me a stick of dynamite!

[Anonymous]

I have done EVERYTHING with my stock 200-6 in my 1980 Mustang to maintain a steady idle. Everytime I get it set, it runs sweet for a couple of weeks. Then I have to adjust the mixture again because it wants to cut off at every light. Yes, I have to RICHEN the mixture.
I can't find any vacuum leaks. It ALWAYS does this. Been doing it for years.
Anybody have a clue what it might be?

 

[CobraSix]

is the idle mix screw moving during those 2 weeks? Each time you set it, close it all the way, and then back it out 2 complete turns. If next time you close it and only turn it 1 turn, then somehow your screw is backing back in. I had that happen somehow once, after a 20 mile drive, my idle mix screw had somehow closed.

GREMLINS

Slade

 

[Lazy JW]

A 1980 Mustang should have come from the factory with lots of smog stuff on it. Is it all still there and functional? CobraSix has a good suggestion about the idle screw.
Joe

 

[Anonymous]

Is that the Holley 1946, or similar carb?

I have to tighten all the screws on mine from time to time. I read on an emissions site once that these carbs are famous for having the 3 screws that hold the throttle body on work their way loose after a while. I should have used loctite the last time I rebuilt it.

Grab the carb and see if it feels a little loose at the base. That emissions site said they have to retighten those screws to get it to idle the way it needs to in order to pass inspection.

I knew I should have bookmarked that site......................

 

[Anonymous]

It's possible that your idle mix screw is not staying put, it's also possible that your carb base is loose causing a nasty vacuum leek. Set all your carb adjustment screws to spec as Slade has suggested, then tighten the carb base, now put a spot of paint where the threads meet the housing and on the carb base nuts. That way if they move you'll know it by the cracked paint. Also, if they don’t move and the problem persists, check your float level with a float gage and with a vacuum gage, check to see how much vacuum you have at idle and check to see if your vacuum advance diaphragm needs to be replaced. One of those should work

Have you checked the timing? I had this happen to a friend once and it tuned out that after he adjusted the timing, he didn’t tighten the bolt at the base of the dizzy and it was moving slightly causing him to think it was a carburetion issue.