I just bought a '96 F150 V8 5.8L Automatic 4x4. Having some trouble. I'm going to go ahead and just list all the problems...

1) Not enough power. (Can't even spin the tires while holding brake)

2) Rough Idle (Already changed spark plugs, wires, ran sea-foam through it, used fuel additives. I'm really lost on this one..)

3) Tires make noise when turning (I don't believe the tires are too big. They are 31' AT, stock right? It is a clicking noise, similar to when kids put playing cards on the spokes of their bicycles. Usually only when I turn hard.)

4) AC blows cold air, but only out the top. (Defrost vent) The front vents only blow a tiny amount of air.

ALSO, I am thinking about cutting off the cat. converter and replacing it with a strait pipe (Don't worry, I don't get inspections.) I know that, for the most part, it is beneficial to the truck (Better HP, mileage, sound, etc) but I am not sure if it is really worth it. A guy at Auto Zone said it can mess up the internal computer and screw up the mileage, but all other sources say the unrestricted exhaust improves fuel economy. What do you guys think?

I'm really excited to get this truck running perfectly, so anything you guys can tell me is greatly appreciated.

Thanks!
Alan

 

Welcome to the board.

I think I can address 2 of your concerns, at least partially.

I have a 1996 F150 5.8L 4x4, stock height, and the door sticker lists the stock tires at 265/75/R15 which is fairly equal to the 31x10.5LT15's that I am running now. My 31's only just miss rubbing on the front valance, so I would imagine that 32's would rub.

If the A/C is only blowing out the defrost vents, then there is a problem with the air blending door behind the dash. The door is not moving when you switch from one vent to another. I am not sure how this door is actuated, but may be a vacuum line gone bad, or if they are controlled electrically, a connection has gone bad.

Good luck.

 

Thanks for the speedy response!

I actually made a typo in my original post, I am running 31's as well. Do yours "click" when turned all the way?

 

About the rough idle....

It could be a number of things. I have a '96 as well and my idle was acting up a bit too. The problem is now fixed though( only after i changed all my sensors and cleaned my throttle body. Ended up being the MAF sensor). If i were you i would check your Idle Air control valve to see if it is gummed up or something. It may even be your MAF sensor that is not sending the right codes to the PCM. A cheaper and more likely solution would probably have to do with your vacuum lines. They have a ton to do with how the idle is, so you might want to check to see if you have any leaks.

About cutting off the cat....

You can do it if you want to but i would remember that there is an O2 sensor right after the cat to regulate your emissions. As much as it sounds like you don't need it, it does send a signal to the engine to tell it to either run rich or lean depending on how much oxygen passes by the sensor. I don't know how your engine may react without it but most of our engines with the EEC-IV systems have a fail safe mode that controls your engine just in case a sensor goes out ( or in this case is not functioning because it isn't there).


Hope my input is helpful.. Good Luck!

 

No, my 31's don't make any noise when turned fully in either direction.

 

For 1) and 2), suggest to get the computer codes pulled. Remove as much of the guesswork as possible. You have OBD-II, so most any chain auto parts store should be able to read them - usually for free.

For 3), suggest to try to duplicate the noise on jack stands. The wheel bearings or the automatic hubs may have a problem. Are the hubs fully disengaged when in 2WD?

4) Agree with dewman - got a vacuum leak in your HVAC circuit or a damper door is stuck. IIRC, there are three doors - floor/defrost, floor/vent, and recirc. The default position is generally to the floor.

Cutting off the cat - the newer models, well newer relative to mine, have O2 sensors both before and after the cats. There is a module available to plug into the rear sensor connector to 'fool' the computer - however, haven't looked around as to how to obtain one.

Arguments both pro and con for taking it off - my opinion is that if the engine revs freely up to 5K RPM under acceleration, the cat is not plugged and money spent removing it will take a while to recoup based on fuel savings. The value of increased performance is a personal call. If it has trouble hitting the higher RPM range under load - the cat MAY be plugged and then it would be worth looking into either replacing or removing.

 

O.k. less than a year ago I got a 93 f150 5.0 auto 4x4. I test drove it around, felt great so I bought it. Hopped on the freeway, and the damn thing wouldn't hold 65 (speed limit 75) .

Now it will hold 75 with 2 atv's in the back, 4 on the trailer behind, both tanks full and 5 passangers.

This is what I did, take from it what you will:

Grabbed plugs, and cap and rotor on the way home. (wires looked o.k.) Changed them out.

Reset the computer, first and foremost, and everytime you change anything..the ford eec relearns.

Next I checked the timing. Was less than 5 degrees, stock is 10. I am running 16 base now. These numbers are all spout out.

I dunno if the throttle cable was stock or just worn out, but it seemed like I was trying to kick the back of the engine block to get it to WOT. I had someone hold the pedal all the way down and I was only getting like 3/4 of the way open on the throttle body. I took a simple butt connector, cut the plastic off and made a spacer and clamped it on the throttle cable. This was the best thing I did to the truck.

Transmission didn't kick down like I wanted. It had to be over 3/4 throttle to kick down. I adjusted the tv cable (I don't think a 96 has this though). Now the kick down is perfect. If anyone tries this, read up on tv pressure and the ford tranny, too high or low can make your day go really bad really fast!

Lifted all 4 corners off the ground and spun the tires over by hand. Any drag from brakes, worn bearings ect will rob power. I have since done both front wheel bearings.

At this point I was pulling the truck loaded at 65 no trailer. I got the truck with 33's, traded for 31's.

Clutch fan. My truck sounded like a jet airplane under the hood. The clutch in fan was stuck, no slip. I threw on a plastic mustang fan and it helped alot.

That netted me 75 with the trailer.

Recently I was at my dad's. Found a good sized subaru electric dual speed fan. Threw that on, and it has helped alot also, but I have not pulled a full load yet. I know it freed up a bit of power, but we will see how it does with cooling with a full load and 100 degrees. My truck never goes above the N in water temp anyways.

Today I did what you had thought about. I cut the cat off (mine only has one, exhast y pipes to a single 3) and the muffler and piping. I piped it back from the y to were the stock muffler was, and added a flowmaster 40 series and maybe 1 foot after then dumped. Contrary to popular belief (especially on this forum) it did add horse power. Most people that say it doesn't or won't, don't know what horse power is. Most think when your in the fast old big block muscle car, and you hammer it, that horse power is what slams you back in the seat, and makes it pull really hard. But it's not HP, that's torque. HP is just a mathimatical number of tq x rpm. Basically it's a number telling you how much tq you have and how long you pull it (RPM).

I'd say yes I lost maybe 1-2 ft lbs tq, but gained HP. Before the exhaust, if I floored it 1st gear would pull 30-35 mph then shift to 2nd. 2nd would pull to maybe 60 mph then start to choke off. The kind were the engine won't pull more rpm, but the trans won't shift, so you let off a bit so the trans will shift so you can pull again. With the exhaust 1st pulls 35, then from 35-40 I notice a bit less pull than before (TQ), 40-50 is about the same, after than the diffrence is huge (HP) and it pulled to almost 75 mph in 2nd and was still pulling.

The thing I worry about is that HP doesn't help pull trailers, TQ does so I don't know if it will be of any benifit. My plan now is to get it to not just hold 75 mph fully loaded and pulling, but to cruise doing it or hold with the a/c on. I hope the electric fan and exhaust will help. I thik I may need to tune (add) the exhaust. Usually you can add length after the muffler to move the power back down, so we'll see.

Oh and I think the clicking when turning hard is your tires rubbing the fenders. Also does your have auto or manual front hubs?