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Discussion Starter · #1 ·
car idles good but when you step on the gas pedal, the car is very jerky and wants to die. I replaced the fuel pump with a Carter and it stills does it. Has a reproduction coil and starter solenoid. The mustang starts up fine and has a 1/2 tank of fuel. The mustang is a 289 with a 4 speed. The car was running good one day and then the next day, boom. Any ideas?
 

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Junk in the float bowl?

Start with a basic tune-up. If you're having a mechanic do it you want to make sure they do:

1. Cranking compression test.
2. Check ignition components, clean & gap points, test condenser, test coil primary and secondary resistance, check ignition high tension wire resistance, clean, gap and check spark plug resistance, check movement of distributor breaker plate (mechanical advance), check operation of vacuum advance. Check voltage drop at coil positive connection. Check vacuum hoses. Set ignition timing to spec.
3. Test PCV valve and check hose and grommets.
4. Check fuel system components. Test fuel sample for contamination with water/foreign objects. Check fuel lines for rust/leaks, including rubber hoses. Replace fuel filter. Check carburetor float bowl for debris. Check accelerator pump diaphragm for leaks and positive "squirt" when opening throttle. Check and adjust choke. Adjust carburetor idle mixture and set curb idle to spec.
5. Replace air cleaner and crankcase breather elements as needed.

If you had acceptable compression in step 1, and everything else checks out okay you should be running a-ok.
 

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I'll add, check the engine VAC at idle too.
 

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What's your timing set at? Might be too far advanced. I believe stock for your engine is 10 BTDC.
 

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Discussion Starter · #5 ·
THE TIMING IS 10 BTDC, the fuel filter replaced, coil replaced, pertonix ignition, looked inside carburator (clean), fuel squirt out in carburator when throttle rod pulled, air filter replaced.
I'm going to adjust the idle & mixture next.
 

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Did you replace the cap/rotor? I had the same issues, thought it was carb issues but turns out the contacts inside the distributor were crudded up.
 

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Would using ethanol gas over a period of time do this?
Not unless it's ancient. More like, you have a tuning problem. Exhaust all of the recent tips, then, report back with your findings, including the engine VAC results. If you are not familiar with any of the suggested tips, let us know.
 
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