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Discussion Starter #1
So i picked up the 89 f-250 5.0 manual. and man did it run rough. So i did plugs wires and cap and rotor with good stuff. now the problem sort of went away but not completely. So I started pulling wires of the cap one at a time and think i found a few plugs that were not running quite right or total at all, what would make a plug not contribute to the running of the truck. What the problem is i have a lack of power, the motor runs rought, idle roughs, has to warm up to be able to even move. burns up gas, kinda expected it. any help here?
 

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Have you looked for vacuum leaks?
You should to do a compression test, better yet a leak down test.
A scanner might help get to the problem too. Watching the sensor PID's might show a slow/bad sensor.
 

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I take it you didn't inspect old plugs for lean/rich condition. Real clean=rich Dirty=lean but you're mainly looking for irregularities in color. You can still do this as long as you have a good hard 20-30 miles on them.

Clogged fuel injectors could be the problem. I've had a 96 Dodge Ram that had the same sounding problem. The crap cleaner in a bottle wont fix it. They had to hook it to an injector cleaning machine thingy. So I don't know what it's called, but it worked. $200 and it felt like a new truck. Could also be a fuel injector failing.

If you want to rule out plugs then try this. With engine off, starting at #1, pull the plug wire from the plug and move far enough away so spark won't jump. Plug in an old working spark plug to make sure you are getting fire down to the plugs. Start engine. Better or worse? Reconnect and move to #2 and so on.

The one that doesn't change will be a bad plug as long as the dummy plug you have in it's place is firing. Replace plug. If the dummy plug is not firing then replace wire. Then look at the cap if not fixed.

Good luck.
 

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hey guys, what if the timing was off? or like one of you said, a clogged injector or 2. possibly a vac leak. the leak is the easiest to check. spray carb cleaner along all of the vacuum connections, and around the intake manifold...
also check your air filter(s). small maintenance stuff can add up to seem like a huge problem

this also may sound like a dumb question, but are you sure you put the wires in the correct firing order? i've heard of guys who accidentally put the 351/5.8W order on it. the order should be: 5.0 Truck 1-5-4-2-6-3-7-8
 

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Discussion Starter #5
i did the vacum check ... nada ... timing, dont have a gun yet, but very slowly moved the distributer back and forth with no change ... injectors love it ... will check ... better than valves or rings
 

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i'm not so up to speed on the trucks, but i think they're not far off from the car 5.0's...
 

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Discussion Starter #7
hey guys, what if the timing was off? or like one of you said, a clogged injector or 2. possibly a vac leak. the leak is the easiest to check. spray carb cleaner along all of the vacuum connections, and around the intake manifold...
also check your air filter(s). small maintenance stuff can add up to seem like a huge problem

this also may sound like a dumb question, but are you sure you put the wires in the correct firing order? i've heard of guys who accidentally put the 351/5.8W order on it. the order should be: 5.0 Truck 1-5-4-2-6-3-7-8
yeah, got out the chilition which was out there with me ... i double checked and triple checked and thats the right order
 

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like i said, it could have been a dumb question, but you never know. I'll let the other guys with way more expertise take this one...

Good Luck!:cornut:
 

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Discussion Starter #9
like i said, it could have been a dumb question, but you never know. I'll let the other guys with way more expertise take this one...

Good Luck!:cornut:
but at least were both learning ... this is a stumper for me ...
 

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Discussion Starter #12
listen to this guy, he really knows his stuff most of the time, kinda, sorta...:shocked:
yeah im afraid to do a compression test! but gona have too, or just fold take it to ford and let them discover what is up for 80 bucks
 

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What's the history of the truck, was it sitting for a few months, years and you brought it back to life, or was it a daily driver?

To clean the injectors I would fill up the tank with Chevron 91 octane (or what ever is the highest in your neck of the woods) with Techron and go through the entire tank, it worked on my truck, and that's what the dealer mechanic/technician recommended. I doubted it but it worked.

Also new plug wires don't necessarily mean good plug wires, same goes for the plugs. Did you double check the spark plug gap, are they the right plugs?

I would also try one thing at a time, no matter how tempting it is to muck with it all, that way you will know what fixed it.

Replace the fuel filter, cheap and easy right?
 

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someone once told me that ford trucks are the only ones that can handle SeaFoam. i've got an 85 5.0 in my Fairmont, and it had no problems with it, but i also have a carb.
did the same with my ex's SFI 300 inline6 from '92 F150, worked like new after that. should check with others about that one. caused the same ex's toyota to seize right up(did that one on purposes:devil:)
 

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Discussion Starter #15
What's the history of the truck, was it sitting for a few months, years and you brought it back to life, or was it a daily driver?

To clean the injectors I would fill up the tank with Chevron 91 octane (or what ever is the highest in your neck of the woods) with Techron and go through the entire tank, it worked on my truck, and that's what the dealer mechanic/technician recommended. I doubted it but it worked.

Also new plug wires don't necessarily mean good plug wires, same goes for the plugs. Did you double check the spark plug gap, are they the right plugs?

I would also try one thing at a time, no matter how tempting it is to muck with it all, that way you will know what fixed it.

Replace the fuel filter, cheap and easy right?
She was a sitter, sat for almost three years, the guy i bought her from would fire her up to head to the dump but that is about it. as for sea foam ill ask ford tommorow about that, i have a freind who is a service manager at the dealer, hopefully he'll know best.
 

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Sounds like a frankenstein to me. I would have ran when I saw the 302 in an F250, afaik, ford never offered the little V8 in anything heavier than an F150 for good reason. Just for grins, have you tried the 5.8/351 firing order?
 

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I agree with 80 maytag, it's worth a shot. There are 2 firing orders for a 302 if someone added a aftermarket cam, you can get either firing order.

1-5-4-2-6-3-7-8 302 standard
1-3-7-2-6-5-4-8 302 HP (same as 351)
 

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Sounds like a frankenstein to me. I would have ran when I saw the 302 in an F250, afaik, ford never offered the little V8 in anything heavier than an F150 for good reason. Just for grins, have you tried the 5.8/351 firing order?
Actually, Ford did sell the F250 with a 302, my dad still has his 87 with one, he bought it new off the lot. I'm leaning towards injectors myself on this little problem.
 

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couldn't screw anything up much if he did try the firing order first. it's cheaper...
 

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The firing order for tucks is 1-3-7-2-6-5-4-8 with a 5.0
 
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