Sputtering and Stalling...

[LEB Ben]

Alright boys and girls...the Bronco saga continues from yesterday. About 15 seconds before the tire blew, the Bronco started stuttering reeeeally bad. I had assumed the tire was throwing chunks and screwed with the fuel line or fuel pump.

So when I'm done with the tire last night, I hop back on the highway, issue is gone, I hit 70 with it, no problems. Turn around to head back home, hit 70 for a couple miles and the sputtering returns. I backed off the speed and found out I could coax the rig to 60mph...applying no more than 1/4 throttle. Anything more, and it would start sputtering and/or stall out. The allowable speed and amount of throttle I could give decreased the closer to home I got...I was barely more than 35mph the last couple miles on back roads. So I was still thinking fuel pump until I got home. When I pull in the driveway, in park and neutral, I give it absolute hell with no issues. I don't see any leaks from the line, I have good pressure coming from the pump, fuel filter has no obstructions.

What I do see is the front seal on my intake is pretty wide open, creating a vacuum issue (and leaking oil)...but I've driven the thing seal-less there before, leaking like a sieve, with minimal issues.

The other thought I had was...I've had alternators do this same thing to me, when they just start going bad, give the battery enough charge to start just fine, but don't have enough juice to run the vehicle and then it starts acting all wonky as it has to draw power from the battery.

I haven't put a light on it yet, but thought there might be a far out chance it jumped time a tooth or two. I find that hard to believe it's running too well at idle, and no issues when in park or neutral. And the cloyes double roller is less than 3 years old.

Help please...thought, suggestions, opinions??????

 

[SuperCab]

If fuel is ok I'd think electrical... No load = no problem... Going down the road it'll complain because of the load...

Timing I would all but rule out..

 

[sgarver]

I would also rule out the front seal on the intake. It only seals the top of the crank case to keep oil in and doesn't affect vacuum. The sides (head area) would affect vacuum. I would look closely at the carb. It sounds like it worked fine when the choke wasn't open all the way but got bad/worse as the choke opened. Thats assuming you started out with it cold.

 

[fatherdoug]

Even though you said the fuel filter was not obstructed, I would replace it.

 

[LEB Paul]

That 400 turd is doomed, only solution is 460

 

[m78]

Not being able to take the throttle quickly would send me towards the vacuum advance.
How long has it been since its had a good tune up.

 

[bucks77ford]

Not being able to take the throttle quickly would send me towards the vacuum advance.
How long has it been since its had a good tune up.

I was thinking the vac advance also if there is no issues with fuel, but I'm not an expert when it comes to how that vacuum advance and mechanical advance all works with low and high rpms.

 

[DNFXDLI]

The higher the rpm, the more advance is needed Buck...otherwise the spark happens too late.

 

[LEB Ben]

Outside of oil changes...it's been 2 years..which has been about 3000 miles tops. I was wondering how many thought it might be the dizzy. The dizzy was new 2 years ago...but sitting does have adverse effects.

 

[Fellro]

I have had filters be plugged enough to still flow fuel, but not enough, The carb systems will behave that way when the filter is plugging. Injection pretty much shuts down, while carbs will keep going, albeit at a slower pace... I have had them do it initially intermittently, as the fuel holds the crud in place, then when the pressure goes away when sitting, the crud falls out of the way. Then it will move back in a bit after running and start to partially plug. If the filter was obstructed, you pretty much would not be running at all.

 

[fatherdoug]

I have had filters be plugged enough to still flow fuel, but not enough, The carb systems will behave that way when the filter is plugging. Injection pretty much shuts down, while carbs will keep going, albeit at a slower pace... I have had them do it initially intermittently, as the fuel holds the crud in place, then when the pressure goes away when sitting, the crud falls out of the way. Then it will move back in a bit after running and start to partially plug. If the filter was obstructed, you pretty much would not be running at all.

That's been my experience also..........a couple of times.

 

[LEB Ben]

Alright guys...been out at the obx for the last week. I'm gonna jump in to the Bronco today...but how do I test if the dizzy is the problem??? As I said in park and neutral, the rig didn't act the same...so how do it test "under load" in the drive way???

 

[G.O. Stang]

Alright guys...been out at the obx for the last week. I'm gonna jump in to the Bronco today...but how do I test if the dizzy is the problem??? As I said in park and neutral, the rig didn't act the same...so how do it test "under load" in the drive way???

Do a burn out!

Jk, but if you put it in drive and hold the brake and just give it a little gas it'll apply a small amount of load on the engine. Be better if you could drive it though.

 

[Fellro]

If it is at higher RPMs, I don't know a good way in the driveway. Take it on the road and see if it is a consistent speed . When it sputters slow down a bit to see if it gets better. If you have to keep slowing down, it is getting worse. If it stays at about the same speed the whole time, then I would bet on filter. If you are easy on it and it is harder to happen, then try getting into it and see how it is. A distributor issue will be mostly consistent. The filter can vary, especially based on delivery load/fuel need. In essence, what you are dealing with if it is the filter is a restriction. You need more fuel than what the restriction allows, you start to stumble due to not enough fuel. At the rate of usage that is under the max capacity of the restriction, it will run fine.

 

[Fellro]

Double--- Firefox crashed...

 

[m78]

Check the vacuum advance with a hand vacuum pump.

 

[G.O. Stang]

I don't know which kinda of dizzy you're running. But points usually need to be set 2-3 times a year for the best results. I however bought an HEI off eBay brand new for $52. It's been a great improvement. It compacts the entire ignition system and improves the spark. Just a thought. And you can always upgrade it to the accel or MSD coils and modules and its the same as buying their $200+ versions. Saves alot of headaches for not alot of money.

 

[fatherdoug]

I don't know which kinda of dizzy you're running. But points usually need to be set 2-3 times a year for the best results. I however bought an HEI off eBay brand new for $52. It's been a great improvement. It compacts the entire ignition system and improves the spark. Just a thought. And you can always upgrade it to the accel or MSD coils and modules and its the same as buying their $200+ versions. Saves alot of headaches for not alot of money.

It's a '79 so it's pointless. . Sorry, couldn't resist. I would change the fuel filter.

 

[fatheroftwo]

Mine did this,

It ended up being rust in the fuel tank, plugging up the fuel pick-up, and after shutting down, the rust would clear off of the pickup. if the trucks sits a lot, and you did not top off the fuel tank, you may check there.

 

[SuperCab]

It ended up being rust in the fuel tank, plugging up the fuel pick-up, and after shutting down, the rust would clear off of the pickup. if the trucks sits a lot, and you did not top off the fuel tank, you may check there.

That's the first thing that came to my mind