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Canuck Tech
Canuck Tech, Auto Service Technician
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Experience:  Red Seal Journeyman Technician, 20 Years experience
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Ford Bronco: Ford Bronco with 289 engine, runs rough, grumbles

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Ford Bronco with 289 engine, runs rough, grumbles and backfires.

I have a recently restored 1968 Ford Bronco with rebuild engine.

Ford 289 with rebuilt Autolite 2100 2 barrel carburetor. Pertronix electronic ignition was added but recently removed to OEM points. Dual exhaust.

Since last December I’ve had a number of problems leading to this one.

Problem #1: Car completely cut out after driving 60 miles on the highway. New alternator failed, mechanic replaced and was running again, however, it started jerking while cruising. Almost like it was misfiring in a cylinder. Pertronix electronic ignition was still in car.

Problem #2: Carburetor overflowed big time when pulling out of the garage. Towed to mechanic and he got it started without having to do anything to the carb.

Problem #3: Same day I got the car back it started jerking every so often while driving. Car was sucking gas… 3 miles to a gallon max. Thought it was the carburetor.

Problem #4: Let car set a few days then started. Car began running very rough, grumbling, gargling is the only words to describe it. The engine became very loud, like a race engine at the point of backfiring. Engine then cut out and would no longer start. Towed to mechanic and he removed the Pertronix electronic ignition, replaced with standard points and coil, and corrected the timing, he said was 10 degrees off. Car ran great, much more quiet without the Pertronix.. Gas mileage was great. Thought it was fixed.

Problem #5: Car sat for a week. Ran it all day, while traveling at a smooth 55 miles per hour, car began to chug, gargling again, ran rough, like timing was off again. Car then cut out. I let it set for a few minutes, flooded it while trying to start it. Would turn over but not ignite. Eventually started but rumbled, gargled, then back fired. Heavy smell of fuel. Towed it to the mechanic and waiting for diagnosis.

Does anyone know what is going on with this? Could it be that the timing keeps slipping? What would cause that? Frustrated and need help.

Hi there - two Issues I can see - problems with the carb - yes. If it floods out and then appears to go lean, there is a problem with the carb (float or needle and seat). I'm wondering if you have some trash that has made its way from the fuel tank to the carb. I know there should be a filter in there, but it sure sounds like a float / needle and seat issue. Did you put a new tank in the truck?

Now problem #2 - ignition... With a close inspection of the points, I bet you will find an issue. Hard to say what has transpired with the ignition system, but what do you have for a wiring harness? There has to be a resistance wire / resistor in the primary / point circuit, other wise the points will burn up and the coil will overheat.

What about replacing the points system with a Ford Duraspark system out of something newer? If the engine is rebuilt, I doubt that you have a timing chain issue, but I suppose it is possible.

Let's keep the conversation going, and I'm sure we can get the bugs worked out of the Bucking Bronco... Canuck

Canuck Tech and 4 other Car Specialists are ready to help you
Customer: replied 4 years ago.

Funny, Bucky is it's nick-name.

Carb- The main fuel tank was replaced, with a brand new tank. There is a pre-filter on the carb, and they originally checked for something similar but found nothing. I used some Seafoam carb cleaner in the tank just incase. I might need to have the carb rebuilt again, just to make sure.


Ignition- We reused the harness from the original truck, it was in good shape, all the wires were still flexible, no cracking and connections were good. I have a question about the coil, when I bought the truck the coil is sitting on top of the engine, and when rebuilt, they placed it back there. I've always wondered if the coil could overheat with the engine and not work properly.


I'm not with mechanics, however, is the Duraspark an electronic ignition? Also, do you think there could be something with the vacuum between the distributor and the carburetor?


I was looking at the 1968 service manual I have and it says the following under "Misses erratically at all Speeds". Ignition System, High tension leakiage acroos the coil, otor or distributor cap. Defective ignition switch. Excessive distributor cam runout.


Any of those ring a bell?

Is this the original distributer? Wires - sure... cap, rotor, but on a resto I'm "assuming" all of these are new. Distributer shaft runout / wear - yes, a possibility. Maybe the first question here is how fussy are you about being original? The duraspark is an electronic triggered ignition system, that will get rid of the points. I think you need to get the carb sorted, and then deal with ignition. Or, deal with the ignition and then get the carb sorted. Putting the coil in a high-heat area is not a great idea - it produces enough by itself without added to it.

I can find some resources for you if you wish to upgrade to a ford electronic ignition. Was the other system points as well? Canuck

Customer: replied 4 years ago.

I believe it's the original distributor. but with new cap, rotor, etc. They definetly replaced those when taking the Pertronix electronic ignition out. the older hotrodder mechanic who is working on said it would work better, and it did.... very smooth until the problems started. Not too fussy about being original, just so that it is reliable. Doesn't seem either at this point.

OK - so is the truck with old hot rod mechanic at the moment? From what you've told me, the carb needs to be dealt with - possibly float and needle and seat, and the ignition needs to be checked out - is the point gap ok? are the points burnt? Is there a bunch of play in the distributer shaft? Does the ignition system output a nice blue spark with a spark tester? Hot rod guy should be able to help you with the ignition system - I wouldn't have points in a car in this day and age... Did you have a chance to check out that link I sent you? Canuck

Customer: replied 4 years ago.
So the mechanic said the new points they put in a week ago were bad. The truck is running again. Is there anything that could be prematurely burning out the points?

Premature point failure - high voltage - there should be a ballast resistor in this system. If the capacitor is the wrong rating, the points will burn out quickly - the old rule was "pit on the positive means over capacity" referring to the microfarad rating of the capacitor. Wow - really old tune-up stuff - I can probably find a diagram tomorrow morning to check out the ballast resistor and wiring, and maybe even a condenser spec. Canuck


I just had a thought about the points burning up. What type of coil are you running? If it is a high output, low resistance primary circuit unit, that could kill the points