Sluggish '99 7.3 - Ford Powerstroke Diesel Forum
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  #1  
Old 05-20-2007, 04:46 PM
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Sluggish '99 7.3

My '99 7.3 is having problems; running rough and sluggish under load or heavy throttle. This problem seems to only happen after the engine has warmed up and been driven a few miles. It is an automatic trans, and when cruising along at say, 50-60mph if you step down hard on the throttle, it will downshift but will not accelerate like it should. It just slowly picks up speed, and if you are going up any kind of incline you can forget about gaining any speed at all. Sometimes when this happens the engine will run rough and sort of skip or cut out, and sometimes it doesn't, it just doesn't seem to have any power. I just had a new fuel filter and air filter installed less than two hundred miles ago along with oil change. This is the second time that this has happened. The first was about a year ago, and I took it to the Ford dealer locally, they said that it either had water in the fuel or trash in the fuel. I ran some diesel octane booster and injector cleaner through it and is has ran fine since then, but now is happening again. I'm just wondering if it could be water or trash again or if it could be something worse?
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Old 05-20-2007, 05:53 PM
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It's not uncommon to get some bad fuel with a high water content in it, as well as any garbage that has built up over the years, and that may be the problem you are up against, You can drop the tank fairly easy in these trucks to clean out the tank, and while your at it, you could do the hutch and harpoon mods on it as well. These are pretty much very low expense mods, but also help to eliminate any chance of air in the fuel system coming from the tank itself, and as a added bonus, you will find filling the tank to the top much easier as well. If you need any links to do this just let me know, and I can get you some.

Gord.
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Old 05-20-2007, 05:57 PM
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You might also want to check inside the fuel bowl where the filter sits and see if yu have a black residue forming in there as well, that would be from the o-rings breaking down.

Gord.
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Old 05-20-2007, 06:03 PM
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One thing I didn't mention is that even though this truck is a '99, it only has 75,000 miles on it. I bought it new in '99, and it is only drive maybe 100 miles per week or less. With this low milege, I wouldn't think that this could be an injector issue, or could it be? It started doing this shortly after the last fuel fill-up. It is just now down to 1/2 tank on that same fill-up. Would it be best to go ahead and drain it, or run it on down to almost empty and then re-fill it and add some octane boost and injector cleaner?
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Old 05-20-2007, 06:23 PM
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No octane boost. You want Cetane Boost!! and yeah wouldnt hurt to run some cleaner through it. You could try it now. Fill up and add some Cetane boost/cleaner and see if it helps any.
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Old 05-20-2007, 06:57 PM
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I don't know why I said octane, mental lapse I guess. My concern is only that this is not the first time I have had this problem and I wonder if it's something more.
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Old 05-20-2007, 07:08 PM
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probably just the fuel. if it has only happened twice over a long period I would chaulk it up to bad fuel.
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Old 05-26-2007, 07:43 AM
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Ya, I would agree with John, bad fuel is not that uncommon. When they refill the holding tanks at the fuel stop, it gets all the garbage from the bottom of the tanks moveing around and when you come in to fuel up, you get some in your tank.

Gord.
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Old 05-26-2007, 10:24 AM
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I'm thinking bad fuel also. I know you just had the filter changed. I would drain the bowl, and change the fliter. Then refill the bowl with some seafoam. The add a moister remover and cetane booster to your tank. maybe 32oz of powerservice.The grey bottle

I'm pretty sure this will help a ton
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Old 06-16-2007, 07:28 PM
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Okay, I have ran two complete tanks of fuel through this thing now, both with cetane boost added. I have replaced the fuel filter and the air filter as well. Still having the same problem. When this truck is cold, or first started up, it runs perfect for like 30 miles. Then after that, it's like it just totally gives up. It doesn't have any bottom end at all, it takes forever to get up to 50 mph. Then if you running along at speed and start up any sort of incline, it just can't get out of it's own way, it's like your pulling a 20,000Lb. load behind it. Today it happened, I was running 60mph and started up a very slight incline, I had to hold the throttle on the floorboard to even maintain 50mph. I CANNOT figure this out........HELP PLEASE. I am supposed to take this truck on a 1200 mile trip one week from now.
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