USAIRPOWER

Hello everyone, I am a new member here. Ive been looking for an extended cab full size 4x4 truck for a while now. After much contemplating I have decided on a late 90's f150. Luckily there are a few for sale, I'm just trying to find the right one for the right price. there is one in particular that seems to be a great deal. The only issue i have with it is that the previous owner "rebuilt" the top end and did not put the exhaust back on, he apparently lost the piece going from the headers to the y pipe. And now the truck will run great (very very loud obviously) but it begins to loose power at about 35 mph. And continues to be down on power at higher speeds. Now, I have been working on cars for a good 5 years or so now, just as a hobby. Mostly fixing 90's volvos and vw's and such. Done a few LR's but this is an issue I have not come accross. My worry is that I will buy the truck and get some dual pipes welded on and then it'll still die at 35 mph due to some weird electrical issue or something else that'll take me months to diagnose and repair. And Id rather not do that. So if you all have any ideas that'd be very much appreciated. Thanks gentlemen (and ladies I'm sure)

2003XLT

I'd say with the lack there of any kind of back pressure it's not able to keep a strong idle maybe surging while running if say for the right price buy it what's the specs? Miles year motor gimme the goods brother

USAIRPOWER

Its a 1997 f150 w/ 4.6. 5" lift (not too keen on that) 33" tires (pretty worn but I already have a set of lightly used duratracs someone wants to sell me) interior is good and body os good. Top end was just redone and granny was remand about 1k miles ago. It seems like a great buy. But as I said, I'm nervious its more than just backpressure. Ive done this before with a 2.0 vw but that is significantly smaller, I'm gonna put some steel wool ***** into the manifold opening and tie it in there with some wire. And we'll see what that does. But I wont see the truck for another couple days. Oddly enough it idles and runs fine up to 35mph and then is when it starts going screwy. Thanks for the help sir.

2003XLT

I do like that idea as far as the steel wool to eliminate the back pressure argument I would buy it regardless of that it may be just as simple as finishing the exhaust or maybe the intake I'd buy it but as far as it not being able to run past 35mph and it possibly being a headache as is I'd pay not a penny over 3k as it sits and if he wants to finish the exhaust and prove that it is just the exhaust at fault then I would give him his asking price but you are taking all the risk there is no need to lose your shirt over a truck if your around the Boston MA area I'll be more than happy to help you out

USAIRPOWER

Unfortunatly I am in Kentucky but considering that im pretty sure im gonna get it (for under 3k). Im gonna take it up to my exhaust shop (i dont weld well) and have them slap something on there (maybe some straight pipes with a couple flowmaster mufflers) and if that doesnt fix it Ill definatly be on here alot asking questions. So ill be appreciative of any help that comes. I need to get the truck and start fixing stuff before I can figure out whats wrong. Im a bit more comfortable about it now that im a member here so I have a few knowledgable people behind me instead of being up a creek alone on it. As long as the motor runs well and the tranny and transfer case work well I think ill be good, anything else shouldnt be too bad of a fix. Thanks for the help. Ill let you know what happens when I go to pick it up.

kgintner1

What about fuel pressure/fuel filter? Maybe it's not getting gas it needs

udderbrudder

What I get from this is that the owner did the top end of the engine to try to cure this symptom. It was misdiagnosed and now rather than find out what's actually wrong with it, he wants to dump it.I'd be making a lowball offer if anything. At higher mileage it's not recommended to do only the top.

USAIRPOWER

That is an interesting idea. Ill ask him, he's a young kid. Ill be sure to grill him hard about it and as i said I think im gonna use the steel wool to diagnose a bit before I buy. It seems though to do with the speed, which sounds to me like an airflow issue. It runs great in nuetral and 1st and 2nd gear, just up above 35 it still runs fine its just down on power. Almost like it is sucking in fresh air on the exhaust cycle instead of dumping the gasous filled air.

kgintner1

Is it a transmission problem?

USAIRPOWER

It runs and shifts well, just without umph. Its still got power just not alot. Like I said, I cant really speculate too much without having it infront of me and being able to test it. I havent worked on these 4.6's too much, do they have a fuel pressure valve at the top of the motor? Im gonna test the fuel pressure before I buy it along with the steel wool idea. Any other testing ideas? How would you recommend me testing the tranny. Supposedly it was just rebuilt 1000 miles ago, but im not a trusting man.