Hey folks I have a great little Bronco 2 that seems to have an issue that I nor 2 other mechanics haven't figured out. So any suggestions. 1st off motor and tranny seem to both be in great shape mechanically but this past weekend i was traveling down the road at about 45 mph when I started up a bit of a grade and as seems to be normal with these older small ford engines it instantly goes into a strain, but this time it began backfiring and blew apart rotor button and destroyed inside of distributor cap. It did this once about 3 months ago and did the same thing have had 2 separate mechanics help on this and it seems to be fine until I hit a strain and then be prepared its going to go off like a canon. Any ideas. I don't consider myself an idiot and have had 3 of these bronco 2's loved them all but this ine has me stumped.....

 

Without being there to see what condition the rotor was in, this is really curious. I've never heard of a Bronco-ette or the Ranger doing this.
If the rotor is just destroyed, then look to the distributor bushings. Could they be worn and possibly be letting the shaft move a bit?
If not, then it's conceivable that the coil could be doing something odd, but like I said, I've never heard of this.

 

Something additional you could check,
Make sure the spark plug wires for any cylinders that fire next to one another in the firing order are separated and not running parallel to each other. It's a long shot, but after you checked greasemarks advice it's the only other thing I can come up with at this time.

 

The first time it happened the rotor button actually cracked almost in two from placement screw(?) half way across toward other placement screw(?) and blew or ripped one of the placement screws out of its hole. But when it happened this past weekend all it did was break the Metal tongue off rotor and put a gouge on inside of distributor cap. I spoke with another friend today who like me has pretty much always drove Ford pickups and his only other possible idea was like yours Coil issue. So that will probably be next thing to try.

 

I can understand chasing a wild goose, but if the rotor is allowed to move out of it's area of rotation and contact the terminals of the dist cap, I don't see how anything the coil can do accomplishes this. There has to be wear in the distributor to allow the gear on the camshaft to push the dist shaft up enough to hit the terminals in the dist cap.
Suggest pulling out that dist and examine it very carefully for wear. Some distributors had a spacer/washer between the gear and the dist housing to limit how much the dist shaft could rise up. Might be worth checking.

There is also something to be said for using genuine Motorcraft parts.
Many aftermarket dist caps and rotors come from the land of chow mein and can bring grief with their installation.

 

Distributor has been replaced and at first thought possibly it was defective so replaced a second time. It has been checked since then and not only by myself, as I'm no mechanic by any means but am fairly thorough and handy at working on vehicles as it is something I have always enjoyed doing, but by 2mechanics from 2 different shops both of whom felt like distributor was fine upon examination I actually believe one of them spoke like it sounded wore and possibly loose but he inspected it and found nothing out of whack by sight, feel or by his examination. But I also want to say I'm not disagreeing that it could be that but after trying it twice I hope it will be something else... Plus I may should clarify the rotor, where it screws onto the top of distributor , is not loose or anything this time but the metal tongue or whatever it is called is gone off the rotor button. I am just wondering what else could be causing this type of issue almost like it is building up pressure when in a strain and popping off(back firing). One other thing I may not have mentioned is who ever had this Bronco before I had it did something strange at least to me and put a performance holley carb on there which to me made no sense for the vehicle. Possibly a connection to that? I don't know but will be investigating cause if not fixed soon this "bronc" may soon hit the boneyard........

 

And p.s. I totally agree with using motorcraft parts on it when able...

 

I've heard of tough issues, but I must admit, I'm blown away.
I will admit the idea of a coil being a really longshot, as it didn't convince me, and I wrote it.
But really, I can't imagine anything that would cause this; but I thought a little harder (aren't you proud of me, Hanky?) and was wondering if the cap fits on correctly (screws not crossthreaded, cap not warped. Of course, that's negated by the fact that 2 different distributors have displayed the same problem.
Therefore, whatever remains must be the problem, no matter how remote.
I'm sure you've had many different caps and rotors on this, but maybe trying a different brand might help (if you haven't already).
And there is something else in my mind. Sometimes, motorcraft will wind up making a generic part that will then fit many different applications and work on 75 percent of them.
This could be the one model (especially as it's a 2.8L with the dist. at teh rear) that is different. It might be best to switch around and see what else gives. I have no other relavant ideas.

 

1 preacher,
Are you doing the work yourself or are you having someone else doing it?
The reason I ask is because there are times when ; yes I checked this/that and it was fine are words only.
I still have to go with greasemark's theory of the distributor and possibly where it was purchased.
What you need to do is remove the cap and rotate the crank manually and watch that dist for what is happening. Something is allowing that dist shaft to jump up or out of its normal area of movement or as greasemark stated aftermarket brand of cap and rotor change might be considered. Something is taking place under load and that's where you have to get the system to see what is going on. As we know there is always a reason for what is happening, we just have to have the patience to chase it down and find it. This is one of those things where the mechanical movement is quicker than the eye. Can you post some pix of these damaged parts so we can see them?

 

Usually work done by me, but due to the fact that it the answer eluded me I had taken it to 2 different mechanics that I use occasionally and this time I may end up having to take it elsewhere. As far as pixs i don't have the old (1st) rotor/cap anymore as for the new ones I will try to do so.Patience I have for the auto but continual finances may be a different story. But I do greatly appreciate these ideas and hopefully this evening after work before church I will have the opportunity to inspect again.