New Bucking of my 77 Bronco with a 302

[Bronco4surf]

Hey Everyone. I've had my 77 for about 6 months now. All was running fine. All of a sudden, it is starting to buck a bit and hesitate under load.

The only major thing I did was add a new auxiliary tank. I have switched between the two and was wondering if maybe in some weird way, I introduced air.

Took it out yesterday and it ran fine. Even under load.

I have not changed plugs or anything since I got it. Only put about 2,000 miles on it so far.

Any advice?

Thanks!

 

[DirtDonk]

Hey surf, welcome to classicbroncos!
Can't be air doing it I would not think, as it would just purge out under normal use in the carburetor. Or is yours fuel injected? What all has been done to it?

when it bucks, does it want to stall, or is it just not accelerating well at that point? does it clear out for awhile after you let off the gas to cruise?
If it's just a short duration thing each time you accelerate, it sounds like you have a carburetor and the extra fuel that's supposed to come from the accelerator pump is not getting there. You've still got gas in the carb or it would not run at all. And if air was causing the pump not to pump, same thing would happen. No fuel at all, or intermittently and it would still run.

i suppose with a carburetor another thing that can happen is gunk from one tank, or bouncing around off road can mess with the float level and if it's far enough off it would effect acceleration. But I've never experienced a float level issue in all these years, so that seems low on the list of culprits unless the carb was not adjusted properly during the last rebuild.

The vacuum leak thing seems like a good angle to check too. If you've never done this let us know as there are several ways of doing it. Some are extremely easy and pretty much sure-fire.

Good luck. But let us know more about your rig.

paul

 

[AZ73]

Clean your fuel filter. I added a tank and didn't think to clean it out first. I had to pull it and wash all the junk out of it and change my filters.

 

[jckkys]

The accelerator nozzles have tiny holes in almost any carb. The OE '77 2150 has nozzles that I believe are less than 0.02". Ford never marked them like Holley or Carter (Edelbrock). The smallest Holleys are 0.021". So it doesn't take much to plug or partially plug one up. It sounds like the blockage may have dissolved or passed like a bladder stone before you drove it yesterday. See if the problem returns before doing anything.