66 Mustang shuts off

Check your fuel pressure.

Sounds like your idle adjust is set too low on the carb.

From: u23084@uwe (Carolina=A0Girl)

I have a 1966 Mustang with a V8 289 engine. It was recently tuned up and was running well until this weekend. Now, it cranks easily, idles a little rough, and operates fine at a high speed. But when I let off the accelerator, the engine cuts off. If I deaccelerate and put it in neutral and rev the engine, I can keep it going. But as soon as I give it gas, it shuts off again. Any idea what is going on? Thanks.

=3D=3D=3D=3D=3D=3D=3D on the old carb units, there are six individual systems that make up the carb. they all work together, and when one of the systems act up, we tend to say the word, 'carb' instead of the single system that is giving the trouble.

as you have pointed out, everything is working except the idle system. that is where you need to look for the problem.

you say if runs fine when you are using the partial and main metering systems, the accelerator pump system, and full throttle system.

what happens is when you let off the gas, is that it shifts the responsibility of the carb back on the idle system, which it is failing, thus causing the engine to die.

some of the problems in the idle system, can be everything from mixture screws out of adjustment, fuel bowl level is not correct, (included in this is dirt sticking the needle valve open), or to much air mixing with the fuel (leaking gaskets) there are more things that can cause this, but this is a start. hope it helps.

~ curtis

knowledge is power - growing old is mandatory - growing wise is optional = "Many more men die with prostate cancer than of it. Growing old is invariably fatal. Prostate cancer is only sometimes so."

accelerator pump...small diaphragm on the front of the carb..spits a measured amount of raw fuel into the systems to overcome the tempaory lean condition when you step on the gas pedal.

We need more info to help more. Need to know what kind of carb you have for more specific instructions on what to try. Do you have a 2bbl or 4 bbl? Is it the original Autolite, or a Holley, Edelbrock/Carter?