My Bronco is a 89, 302 V-8 AOD tranny.
I will try to explain this as good as I can.
My Bronco drives perfectly under most conditions but the only time I have problems with it is under a load and only somtimes.
If I am driving along and start to go up a hill I put my foot alittle harder on the gas to hold speed, now it might take 1/4 mile or so but then it starts to miss to the point you begin to loose speed and then gets BAD and the only way to keep up is it to force it to downshift and even then you have a bad miss. Now when you start to level off and let up on the gas the miss goes away. I had this problem once before and Ford put $600 worth of parts and labor into it and the problem was still there so I called them back and they looked at it and said it needed plugs,wires and distributor cap for another $200! I said no thanks I will do it myself and I did, when pulling one of the plus(sorry for this dumb explination) the part that goes into the cylinder was broke off, not the electrode but the insilation. After changing the plugs and wires(and distributor cap) all was well and no more miss. After a few months it started missing again. I put up with it for awhile and then decided to pull the plugs and have a look and nothing appeared wrong. While the bronco was in for a valve cover job I had my mechanic replace the plugs and wires and it fixed the problem......for a little while!!!!.The biggest problem I have with this is when crusin on the highway, and going up a hill above 50-55. I don't have a muffler and you can hear a slight backfire when it is missing. Like I said the problem only happens under load conditions and it takes 1/4 mile or so for it to start missing. I know you are supposed to change plugs and wires every now and then but not every six months!!!!!!!!!!!!!!!!!!!
Any ideas what this might be????

P.S. Sorry for the long post

 

i take your use good quality plugs and wires, right?
that cheap stuff isnt worth the effort IMOP, when it starts to act up if you start slowly backing off the peddle does it get better? if so check your fuel filter, it maybe starving for gass under load, you may want to look at a higher energy coil or ignition modual like a MSD, just some things to look at. DW

 

sounds like you cat is clogged up. this can cause over heating or loss of power on hills

 

As for the cat it is not clogged, clean all the way through(with no muffler I can see) Now as for plugs and wires I don't get the best but I don't get the cheapest either. I will look into new plugs, wires and a high energy coil and or ignition mod. What gets me is when you are going up hill it takes 1/4 mile before it starts to act up. The last time it acted up was a few months ago I had to remove the muffler and I just never put it back on(sound better with it off ) and after taking the muffler off it never did act up again(whiched seemed strange) and my gas mileage went up(from10mpg to 11mpg ) then yesterday I was going to Canton Ohio for some business and WHAM going up the one hill it started missing but did not loose speed, then came the next hill and it stared to miss very bad, this time I had to force a downshift(If I didn't it will slow all the way down to 40 before shifting out of OD even with a WOT) and it was still missing and was a struggle to hold speed but as soon as I got to the top of the hill and let off the gas it cleared up and all was fine. Coming home it did the same thing but after getting over those hills I was crusin along at 70-75Mph with no problems. By the way, when I say missing, the whole Bronco will start to SHAKE BADLY but take your foot off the gas and it is ok. And now that I think of it, I was getting some gravel for our drive way about a month ago and I was towing about 3 tons in overdrive and holding speed and it did not act up(no hills though but still quite a load). I will get a fuel fiter and try it again, last time I did replace the fuel filter first and it did not help at all. And now that it was mentioned, my fuel pump is quite noisy at times, could the pump be going bad and starving the engine of fuel under some conditions??
Thanks guys!,
Kevin

 

yup i could be wrong, dont tell anyone if i am! but kinda sounds like fuel starvation problem when it comes under load, get a fuel pressure gage your sytem, you should have two fuel pumps, low pres. pump in the tank, that feeds the high presure pump on your frame rail under drivers door. yor low pressure pump may be weak, bad, or low voltage, if the voltage to the pump drops, so will the volume. could be bad regulator, check the vacume line to the regulator it should increase the fuel pressure under aload. just some stuff here to look at, hope some of it helps. DW

 

One other thing to try especially if your in a warm or hot climate is to bypass the water lines going into your throttle body. Mine does this same thing when it's hot and all it took was that to bring things back to normal.

 

I have not had time to look into the furl situation but I did pull the trouble codes. Key on Engine off I get 11--PASS
Key On Engine Running I get 44-Problems in thermactor Air COntrol system. and 52Power Steering Pressure switch.( forgot to turn the steering wheel when testing) and lastly I have 77-Operator Error During Dynamic Response Protion of Engine Run Self Test.
I live in Atwater Ohio. the last few days it's been rather warm in the high 80's to low 90's. This problem happens when the engine is running at normal operating temps. But happens in the winter, summer, spring and fall.............But I did notice when it happend the Bronco was running about 10 degrees hottter than normal(210 instead of 200) And while I was pulling the trouble codes I have I would guess three different cylinders that have a miss in them. Maybe time for a tune up.........(with good quality products)

 

WEll I have taken the distributor cap off and the coil distributor wire off and they haver a WHITE corrosion on them. I took the cap off and off the the points have this same WHITE powdery corrosion on them. I think this might be my problem, the wires and cap that is on there is about 2 or maybe 3 years old. What would cause the white corrosion?? Water?? how could it have gotten in there?
Thanks for the help,
Kevin

 

definatly tune up time. it should be done at least every year if not more to keep things in tip top shape. I bet once those are replaced your problem goes away.

later

 

Well seems I have fixed the problem,
I found some things out in the process. When I pulled the plugs turns out when I bought plugs last year I bought the wrong ones for my mechanic to put in and they were not even gapped right(he never checked). I had AutoLite 26 instead of 25's(don't look like much difference) but the Gap on my 302 should be between .042-.046, the gap on the old plugs was less than .040!!
So I put New plug wires in(AutoLite Professonal Series 8mm), New spark Plugs(AutoLite Copper Core Gap set to .045), new Distributor cap and rotor(both made by Wells). Really has helped the power, My acceleration is not any better(what do you expect from a 6,060lb SUV) but the tourqe seems better, starting from a stop is not as hard and the missing under load has stopped. I have to haul about 2,000lb of gravel on a 2,000lb trailer tomorrow so I will really find out if it is fixed.
Thanks for all the help! I sure am glad to have this fixed, it's terrible when your BABY is sick and ain't runnin right!