Thread: Choking at 1000-2000 rpms

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for a 65' mustang im gunna guess it's stock? if it is it's probably got the 2100 motorcraft carb on it. they were common in that era of mustangs. and since you backfired the car the first thing i would go to is the pump diaphram. they blow out real easy with any kind of backfiring. i went through this on a jeep a had, changed out everything, fuel pump, filter, plugs, cap, wires, even dropped the gas tank and cleaned it cause the dang thing had just been rebuilt, but low and behold i had another bad diaphram from a small backfire when installing and setting up the new motor. it was really frustrating to boot! cause i had every diagnostic test done on my ignition system i could think of, replaced everything (course it was due so i wasn't too miffed going to NAPA) but as it would turn out the power valve again was the issue. after that she ran like new again

Bad gas (ethanol) only takes a couple months to break down 90 days is the shelf life on gas with ethanol (standard at the pump these days) and since it breaks down so fast it doesnt take much to harm the older carbs. all the issues as you describe are the same as my jeep which had the same/simliar motorcraft carb on it. it costs about 20 bucks to buy the power valve at NAPA or 25 bucks to buy the rebuild kit online and comes with the power valve the part number 4008 is typically the 2100/2150 motorcraft one you'll end up needing to get. just make sure you check the vaccum lines before you replace it. sometimes backfiring will also cause one of your lines to go kabloowee. not sure if you need it or not but i can email you a PDF file on the motorcraft to rebuild it. not sure when the last time you rebuilt the carb but it maybe a good idea to go ahead and do that as long as your replacing the power valve. there maybe some gunk from the bad gas (which can crystalize) these particles can get caught up in the jets.