Originally Posted by Conanski

Have you checked ignition timing? Factory base setting is 10deg before TDC with the spout plug removed to disable computer advance but you should be able to add 2-4 deg more.

And you still need to check fuel pressure.. doesn't matter how new the pumps are some of the aftermarket pumps only last a year and others only weeks.

Originally Posted by Crewcabber

Take pictures of the resonator tips and post them. Your exhaust leak is gonna kill you on power. I just tracked down my exhaust leak and fixed it, it was a small leak and it made a night and day difference

Originally Posted by FatherDonald74

My 460 (Under)Powered 1996 F350 4x4 Regular Cab Long Bed is severly lacking in the power department. It use to run really well back in the day and always made my buddy in his 360 powered '96 Ram 1500 look like he was sitting still when we raced. I know my engine is a 460 and his a 360 but at 1200lbs. heavier my truck always made short work of his. I have 285/75/16's and he has smaller 245/75/16's which takes away power from me as well. We both have 3.54 gearing. Anyway, back to the topic.
The truck really started to feel like it was lugging and with only 80,000 miles on it, that seemed too soon to feel worn out. I later discovered that both rear brakes were dragging evenly so it never pulled to one side more than the other, it just felt sluggish.
Fast forward to today. I have long since adjusted the brakes but for the last 2 years it has still struggled. All the tires spin freely but I have to almost floor it in second gear to really take off fast in 2nd gear and the tires won't even spin. Not that I care about burnouts and such but when towing or hauling I feel like I'm better off using my wife's 3.0L V6 Escape. This is no joke. The truck stuggles to pull an empty utility trailer weighing about 1000lbs. up a 7% grade. On this local hill that is about 1/4 Mile long and the speed limit leading up to it is 45mph(going about 50mph before climbing)I have to shift down to 4th halfway up, by the time I'm almost at the top I'll have to shift down to 3rd. At the top I'm doing only about 35mph. Empty I can barely make it to the top in 5th gear.
I swapped in a ZF5 hoping to help free up some power over the C6 that was in it when I bought it but it was really no help.
It has headers and a gutted cat so there are no exhaust restrictions. The check engine light is not on and O2 sensors are not that old. It has an annoying exhaust tick at the headers and the only thing I can think of is maybe it's losing exhaust there and therefor the O2 sensor is not reading the proper amount of O2 and messing with the computer? If that were the case wouldn't the check engine light be on? Besides that, there was a bit of an exhaust tick back when it had stock exhaust manifolds back in the day and it felt plenty peppy.
The truck is a '96 but it doesn't have OBDII because it was made in '95 for the '96 model year. It doesn't have an MAF sensors either.
The only thing I can think of checking is removing the spout connector and checking the timing. Maybe I'll adjust it and see if that helps. I'll also do a compression test to see if maybe I've got a weak cylinder or two.
Any other suggestions would be welcome at this point.

Originally Posted by F-250 WARHORSE

Do a tune up, Check your thermactor air pump, verify your fuel pressure and check the fuel pressure regulator, and do plug wires, cap, rotor, plugs, and maybe fuel lines kinked or something. Mine showed good fuel pressure on the autozone rental gauge, then I checked it with a MATCO gauge and lone and behold the pressure was completely different, so keep that in mind. Also, verify the pressures while driving, not just parked. If pressure is OK but volume is low, then it will suffer. I had similar problems on my truck, same as yours, and put a new O2 sensor in and improved it noticeably, was told and read on here that o2 sensor would not change power but picked up about 10 mph climbing the hill by my house after the swap. Same truck, same driver, same tank of gas, same day, same hill, same gear, both trys warmed up, hit the bottom of the hill at 35 in 4th and the top at 55, new o2 sensor, and bottom at 35 in 4th and top at 65 then I backed out of it. I rest my case. Now I am in the process of new fuel pumps, we will see if I can get 70 by the top of the hill.

Originally Posted by F350 1990

Are you operating in higher elevations/mountains? (Timing needs an adjustment -- higher advance -- take it up to 14 if possible)

One issue I see already is a potential imbalance in your exhaust system (back pressure).

Originally Posted by cbakker

Before shooting down anyone else's thoughts or theories, you should check the fuel pressure and do a compression test. Even though your other fuel equipment is new, doesn't mean it is operating properly. Having even a minor exhaust leak combined with leaving the vehicle sit for extended periods of time can be murder on a motor.

Since you've been running it for a couple years like that, even with an open exhaust system, you are getting plenty of buildup in there from running rich(my assumption since you are getting 6-9 mpg without towing). Try a new O2 sensor is my vote.

Originally Posted by F350 1990

cbakker -- exactly. Have to rule out the basics (fuel pressure, compression, exhaust effects on air/fuel balance, O2, etc). I know we've been over this exhaust issue, but the bottom line is there is a fairly delicate (engineered) balance in exhaust systems and I've had plenty of customers drive in with issues involving headers, eliminating cats, etc.

Originally Posted by FatherDonald74

I too have heard of many people causing their engines to throw codes after eliminating catalytic converters or adding headers but in this setup, it's not as sensitive to modifications like others. There is only one O2 sensor and it's BEFORE the catalytic converter so cat or no cat, anything downstream of the O2 sensor will only effect the emissions(which my truck is exempt). Also, I bought factory fit, replacement Hedman headers which keep the EGR intact as it was stock so all is well. The air pump blows fresh air into the catalytic converter to aid in emissions which also has no affect on the way it runs because the O2 sensor is UPSTREAM from where the air pump dumps it's air.
I've driven many EFI 460 powered trucks that had their cats gutted and headers added where power increased after doing so whereas mine was down on power before AND after modifying my exhaust. My exhaust leak at the manifolds is an issue I plan on attending to but as I said before, it has always leaked there since I bought the truck and it pulled like a freight train even with the leak. It lost power BEFORE I modified the exhaust system.
After it lost power I then replaced the fuel tank, fuel filter, fuel pump, and then I checked the fuel pressure with new pump; still it was down on power. I then gutted the catalytic converter thinking it was clogged and replaced the O2 sensor. All these did nothing to help.
I then thought maybe the loss of power was due to a dead cylinder but there has never been any sign of anything foreign in the engine oil. Also, it runs smooth, I mean smooth. It starts right up, idles and revs like a new engine.
I have yet to perform a compression test on this engine since I have been working on other projects and I don't think with only 90,000 miles on a 460, that it could have worn out rings. I've seen 460's go for three times that and have no metal shavings in the oil but anything is possible.
It has no symptoms of a fuel pump dying like hesitation, hard starting, and stalling. The only thing going on is a lack of power.
I'll check the fuel pressure tomorrow to cover all possibilities but it's been a while since I tested this type of engine. I know the proper procedure but there is one detail I'm not clear on. Do I need to ground the number 6 pin on the EEC plug on this later model EFI 460? I don't recall if I did that before last time since it was so long ago and I've had dozens of projects since the last time I messed with this truck.