Off idle hesitation and stalls at about 25mph each time

Hello:

I hope someone can help me with this.  I have a 1970 Mustang coupe all stock except for 4bl Holley Avenger carb.  I have had the car parked for about 3 years, I have had her parked a couple other times also, but she always just fired up and ran.  Just before parking her last time we put on this Holley carb, I'm not familiar with Holley I liked the Motorcraft one but I could not pass emissions.  The car idles fine and it revs up fine in park or neutral, but in gear if you it stumbles and will stall at about 25-30mph. If you let off of the gas just before the stall it will recover and continue to run.  We already replaced the plugs and wires.  I wondered if it is the secondaries causing the problem?  Any info would be great.

Thanks,

Pixieroo  

Parked 3 years..  hmm.... Old fuel...  not enough bang left i the fuel...

can you do a full flow cranking test...  with the IGNITION coil Positive wire UNPLUGGED... so no sparks can be created..

with the carb fuel line disconnected and directed into a clean clear plastic bottle.. 2 or 3 liter..

have somebody crank the engine while you observe the pulses of fuel into the bottle...  each pulse should be nice and full.. equal to the others..  not diminishing..

if the fuel system is restricted at some point.. the first pulses may be full.. then get smaller and smaller to a drip.. ..  this can cause your problem..   dirty fuel filters.. crushed fuel lines.. clogged fuel lines..  sediment in the fuel system reducing the ability of the pump to pull the fuel up from the tank and push it into the carb...

i had a friend with a 67 fairlane with the exact same problem..  he had 2 cars and both had it.. one car the fuel line was crushed by improper jack stand and floor jacks under the drivers floor pan.. the other had sediment in the fuel line..   we used a new universal speedo cable to rod that out with a variable speed drill like a plumbing snake .. until we could replace the fuel lines..

you could just have a fuel pump going south also..  but do the full flow test..



you should get almost a pint in 15 seconds of cranking..  

Hello:

We were also suspicious of the fuel pump, so we checked that there was fuel flow, but not as carefully as you explained, we just checked that it was flowing.  Would the car stall at about the same speed each time if the fuel lines were partially clogged?  I'm going to go down and check it like you suggested.

Thanks!

Pixieroo