Terrible Hesitation

Hello all.  I'm new here and new to fixing my mustang.  I have a 1966 I6 200 automatic transmission with an autolite 1100 carburetor.

A month ago the car was running fine and my wife used it as an everyday driver to and from work less than 3 miles one way.  Then she drove it across town nearly 15 miles and on the interstate for 4 of that going up to 55 miles per hour.  Just as she got to my workplace the car began cough and died.  I couldn't get the engine to keep running for more than 3 seconds.

I had it towed to a mechanic who said the carb was "shot" but I'm pretty sure that the only way to wreck a carb is literally to shoot it, take a hammer to it or maybe drown it in saltwater.

So I instead rebuilt the carb, then changed the points & condenser, then the rotor & dist. cap, then the wires and plugs (which needed it anyway) and finally the fuel pump.

Now the car hums beautifully when idling (as it has done since I rebuilt the car) but hesitates, occasionally backfires, and sometimes almost dies when I press on the accelerator.  As soon as I let it off she purrs again.  I'm at my wits end.  

Any insight and wisdom would be greatly appreciated.  

i have a few tests....  this first test takes about 8 or 10 minutes.. directs us to a LOT of INVISIBLE issues that will drive people crazy...



please post results from the last 4 tests by number.

1.

2.

3.

4.

lack of ground has been a MAJOR issue...

since you have an 1100... can you replace the primary wire from the points to the COIL NEGATIVE..

can you also check the ground strap that runs from the inside of the distributer housing.. to the hold down screw or the upper breaker plate where the points are screwed down to..

remember..    when the points are closed.. electrons flow from the negative battery .. through the ground cable. through the block.. up through the distributer housing, up the ground strap to the base of the points.. across the closed contact... to the primary wire to the negative side of the coil...   this is how the circuit is completed on the ground side of the ignition coil...  if you have any opens you will have issues...

ford really did not design in enough grounds connections in these...

you will be really better off with at least one additional ground connection..

what you should already have.. is

negative battery post to the engine block...

back of the engine to the firewall behind the head...

you need to add a 10 gauge or 8 gauge wire from the engine block where the negative cable is attached  to the inner fender...  with proper ring terminals installed...


you will also want to remove your battery.. count the wires on the battery side of the starter solenoid.. take the nuts of and wire brush both sides of each ring terminal..  wire brush the stud.. reassemble..  count the wires to verify you have them all reinstalled...


you could also have positive power supply problems...  shorted wires under the dash.. bad ignition switch...

if you have a test light...   hook the clip end of the test light to the I terminal on the starter solenoid.. stick the probe end into something thats grounded so you can see the test light from the drivers seat... thats the same as the positive side of the coil...    pull the other push on wire off the starter solenoid.. (S ) terminal..  slowly turn the the ignition key to the RUN position.. you should have a medium bright test light.. as you turn to the cranking position.. you may loose some or all of the brightness..   let the key back to the run position.. you should still have a test light...


do the same with the S terminal connected and start the motor...  this proves the positive side of the ignition coil power circuit works...


this is just a first step in diagnosing your problems that are intermittent..  it is not the last step...

what i have posted might take 20 or 30 minutes altogether to complete and verify...  

You might want to check fuel delivery. A fuel filter that is almost completely clogged will pass enough fuel to idle but not much else.  

may want to check fuel pressure/ volume,,  but have you looked down the bore of the carb, (engine off, choke plate open) and see if the accel pump is working? you should see a spray when you pump the throttle, could be miss adjusted accellerator pump linkage, or a problem in the main jet circuit that is not getting fuel , only off the primary circuit.