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Been having a strange problem lately on the freeway. Once I get up to about 80mph (or 70mph at small incline) the stang starts "hesitating" almost like its running out of gas, so it kinda like jerks back slightly. This will get worse until I let off the gas. Then when I press the gas again, I get no response except a deep sounding "sputtering out" or grumbling sort of noise (sorry I cant think of a better way to describe it :p ) Almost imagine it like your timing was way off or you had a bad vacuum leak, and when you hit the gas, it just makes the deep grumbling noise like its trying to struggle to do anything.

Anyway, it will just do this until I let off the gas for a while (and quickly make my way over to the right lane in a panic! :: ) until I get down to about 45-50mph, at this point the engine will again respond to pressing the gas, and it continues driving on as normal like nothing ever happened. It never dies or anything like that, just kinda waits until I lose a lot of speed to recover itself.

At first I thought it might be timing, so we readjusted that, but it doesnt seem to have fixed it. Maybe points? It only happens at these higher speeds and when the engine is under more stress.

What do you think?
 

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Yeah, I'd check the points first, and then look at fuel delivery.
 

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How about your fuel filter? It might be partially blocked or restricted alowing only enough gas for lower speeds, but not enough for high RPM's
 
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Sounds like you've got the perfect solution for speeding tickets. Maybe you could patent it once you find the problem.

Seriously though, as you describe it "sputtering", I would also begin by looking at ignition. I experienced a similar thing due to the floating points. Do you have a tach and if so what is it doing while this is happening?
 

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I'm guessing it's a fuel delivery problem. I'd start by checking the fuel filter (including any screwed into the carb body) for blockage , next the fuel pump for flow and fuel lines for restrictions. If no apparent restrictions there, check the main circuit in the carb as it may be plugged with gunk that causes the carb to lean out at certain speeds. I once had this problem with a manual choke car and the only way I could keep it running was to pull the choke all the way out. Lastly I'd pull the tank sending unit to check the filter sock in the gas tank.
 

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That sounds like the problem that I was having with my 66 convertible, only it was at 65 mph. I replaced the fuel pump and that moved the speed that it would sputter to about 70 mph. The problem was with the rubber fuel line between the tank and the fuel line. It had softened and bent forming a crimp, just letting enough gas through to allow the car to run fine up to about 65 mph.
Check your fuel line from tank to carb. If it looks good and changing your filter doesn't help you might need a fuel pump. Good luck!
 

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would guess dirty fuel filter and definately fuel starvation. it starts at 70 to 80 MPH now and as it gets dirtier it will decrease to where this is happening. don't forget filter in gas tank but doubt this is your problem.
 

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Your mother forget to tell you she had a 'governer installed' at your last oil change.

No worries though, buy a new fuel filter, buy a new cap, buy a new rotor. $30 or so for all that junk and the problem should go away.
 

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Sounds like fuel filter to me too. Or some part of carburator like one of the internal rubber diapraghms. Look at my other posts for links to sites to troubleshoot "sounds" etc like your describing. Autozone has a good one...many more in my prev posts.Also your shop manual has a chart too...see my posts lol :eek:

One of my more recent responses to a post describes a similar problem I and others had - dirty fuel filter - resulting in hesitation [ and how I FOUND it WAS problem].
Changing fuel filter is a quick way to find out, simple, takes about 10 minutes or less.
 
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