Sputtering at high speeds.

[guevara42]

Hey folks, I have a 66 coupe, 289. Car sputters at speeds starting at 65-70 and gets worse if I try to go faster. I have changed everything I can think of. Fuel filters, fuel pump, I put in an electronic ignition about a year ago. New gas tank tank and sending unit. Anything else you guys can recommend I try? I did notice that I need new exhaust manifold gaskets because i can hear a leak and visually confirmed it. TIA.

 

[MitchGT]

Hey folks, I have a 66 coupe, 289. Car sputters at speeds starting at 65-70 and gets worse if I try to go faster. I have changed everything I can think of. Fuel filters, fuel pump, I put in an electronic ignition about a year ago. New gas tank tank and sending unit. Anything else you guys can recommend I try? I did notice that I need new exhaust manifold gaskets because i can hear a leak and visually confirmed it. TIA.

Clean out the filter in the carb. some have them. exhaust leak would not cause this.

 

[guevara42]

Clean out the filter in the carb. some have them. exhaust leak would not cause this.

Fuel filter has been replaced recently. Thanks,

 

[HookandLadder]

Check your coil. Could be cutting out at higher speed.

 

[rbohm]

start with the basics, and dont take anything for granted, even the new parts you put on as it is possible that even they are defective.

1: check your fuel pressure at speed

2: check your initial timing as well as your advance curve

3: check your fuel flow

4: check your air filter

5: check your plug wires and plugs

6: check your coil

7: check for vacuum leaks

 

[gikort]

What about the float level in your carb?

 

[guevara42]

I will check the fuel pressure and the flow. This only started happening about a week ago. I did put in a new coil about 6 months ago and I think I will try new plugs and wires next. That's the only thing I have not done. Thanks.

 

[WTFO]

What carb and distributor are you running?

 

[guevara42]

What carb and distributor are you running?

Carb and distributor are original. Motorcraft 2bbl carb and the original distributor with electronic point system. Carb was rebuilt less than a year ago and it's been a few years since dist. has been rebuilt. Opened up carb and it's as clean as can be. Thought I may find gunk but it was good. Thanks.

 

[WTFO]

It's vacuum advance then? Bad vacuum pot on the distro maybe? Does the car idle okay? Could be a vacuum leak on the carb somewhere. Bad accelerator pump? Easy way to find a vacuum leak is to start your car and let it warm up completely then using an un-lit propane torch, slowly pass the torch nozzle by anything on or near the intake. If the idle goes up at a particular spot, you've found your leak. It's a pain with a mechanical fan blowing under the hood. Good luck!!

 

[horseballz]

I use a 6-12 inch piece of hose on the nozzle of the propane torch. It allows easier access to the tight spots. I'm guessing your sputtering is due a timing curve issue. Try disconnecting and plugging the vacuum advance and go for a drive. If the sputter goes away or changes, you'll know if you're on the right track. Does the problem happen at the same/similar engine RPM/load regardless of what gear you are in?
My $.02,
Gene

 

[PoppyMod]

Hi,
Check the wires to the "+" and "-" or "Dist" or "Bat" are correct. A polarity issue will cause your sputtering, as well.
As noted, you can be experiencing a lean condition as others have mentioned. Check all of your plugs too.
Good Luck!

 

[Hack]

I noticed that you didn't mention plugs/wires/cap/rotor condition. I have had vehicles with a miss-fire on the highway that was caused by worn ignition parts.

 

[azduffee]

Hey folks, I have a 66 coupe, 289. Car sputters at speeds starting at 65-70 and gets worse if I try to go faster. I have changed everything I can think of. Fuel filters, fuel pump, I put in an electronic ignition about a year ago. New gas tank tank and sending unit. Anything else you guys can recommend I try? I did notice that I need new exhaust manifold gaskets because i can hear a leak and visually confirmed it. TIA.

I once had a little piece of gasket in the fuel bowl that would get sucked into one of the jets at freeway speeds causing the same thing you are experiencing.

 

[guevara42]

I finally gave in and took the car to a pro. I did everything stated by everyone. I changed everything, coil, wires, plugs, vacuum advance, filters. I opened up carb and looked extremely clean. The timing was dead on. Im waiting for a response from the mech. I'll let you guys know what it was. Thanks fellas. P.S.

 

[PoppyMod]

I finally gave in and took the car to a pro. I did everything stated by everyone. I changed everything, coil, wires, plugs, vacuum advance, filters. I opened up carb and looked extremely clean. The timing was dead on. Im waiting for a response from the mech. I'll let you guys know what it was. Thanks fellas. P.S.

Hi,
I would advise, you to request the mechanic, to return any replaced parts and provide a detailed explanation. It can only benefit you in the future.
Good Luck ......Merry Christmas!

 

[guevara42]

After all that, it was a bad distributor. I swapped with a new one and car runs great. Thanks for all your help.

 

[PoppyMod]

After all that, it was a bad distributor. I swapped with a new one and car runs great. Thanks for all your help.

Glad to hear it's fixed.
....and to think in could have been a $3 capacitor?
Happy Motoring!