Hey fellas...the 351M in the Bronco is really starting to piss me off. For the last week or so, there will be times where it will sputter anywhere from idle to 35mph, sometimes even cut out, but if I feather it, she'll come back alive. Then other times, it sounds like it's running on 5 cylinders. Then days like today, it'll run perfectly. I will say though, when it is running rough, the longer I drive the better it starts to run. I just threw a new fuel filter on there, new plus 500 miles ago, the carb, fuel pump, wires are a year old, new timing chain 2.5 months ago. Any thoughts on where to go next, or which of the new parts could have failed?

just a WAG, but can you swap out your ignition box with one you know is good?

or drop a 460 in

I was thinking that and/or dizzy cap too possibly. And for the record...no 460 swap...YET. But my dad is picking up a 400 for her this weekend...so if I can get her home, she'll be rid of the problems.

Back when I had the original 2 barrel on the '79 I had such a problem with keeping the fuel clean of rust that was coming from my rear tank. It was so fine that the filters (yeah I put 2 in line to no avail) wouldn't keep it out. It acted sort of the same, when it needed more fuel (ie: a hill) it would spit and sputter untill you got out of the throttle. I ended up at first taking the carb apart and cleaning out all of the debris every 6 months. Then I put the 4 barrel on and quit using the rear tank untill I could get a new replacement.

So after all that, maybe get a clear fuel filter (if you don't already have one) and see if you have any contamination.

Thanks Lee...I had a clear filter on there for about a year until I swapped it on Monday, and it was about what I would have expected, nothing out of the ordinary. But I do know the tank is kinda dirty, so maybe I should just clean out the carb and clean the tank as well. But before I did that, I wanted to hear any other possibilities.

Sometimes the dirt can get sucked up to the pickup kind of randomly so when you're off the gas it will settle back down and then only come back up at a different time, so that's another possibility.

Captain p4 said:

Sometimes the dirt can get sucked up to the pickup kind of randomly so when you're off the gas it will settle back down and then only come back up at a different time, so that's another possibility.

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Just pulled the tank in my mom's old van due to that...then we sold it 2 weeks later

Id do that and then if it dont work get a new ignition box or upgrade to msd or mallory. I did that on the 76 and it worked great and was very easy to install. I had troubles with the original ford box, tried a new one and same problem.

I bet on the ignition box, i had the same exact symptoms on a 351w i had....

Also, i was going crazy cuz i bought 2 that were bad from the factory.....

Thanks Joe...good to see ya again.

sticking accelerator pump on the carb?

double post

I would have to agree with the dirt in the gas, but I would think you would have seen something in the clear filter if it was on there for a year.

Damn...where did my 'fix' post in this thread go?????? Anyway, thanks for the tips guys. What ended up happening was the ear that get's clamped down on the back of dizzy cap was broken off allowing the cap to shift, as well as two of the 'contacts' inside of the cap were completely gone...the rest were almost non-existant...and the rotor was corroded and rusty.

Oh man looks like we need to go dump some dirt in your tank so that our answers could still be right

Glad you got it figured out Ben

Whoops...just realized I created two very similar threads, and the fixes in the other thread fixed this too.

UTfball68 said:

Whoops...just realized I created two very similar threads, and the fixes in the other thread fixed this too.

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You're just trying to get to 10k posts quick that's why you did it!

73F100Shortbed said:

You're just trying to get to 10k posts quick that's why you did it!

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Shhhhhhhhh...you'll blow my cover...honestly though, I forgot all about this thread, or I woulda just posted it in here.