Huge Power Loss On My Ford F-250

when not in gear, i wonder if perhaps there may be something actually "holding" you back ? your comment about feeling as though you were towing something huge made me think of a situation i had encountered once where the emergency brake was applied and the brake light inside was burnt out and since my friend "never used" his emergency brake, he never thought to check it. same symtoms, same problem description, drive your truck and see if front wheel centers are getting too hot which could implicate a caliper sticking, just a wild shot but i know for a fact that this is possible..

Already checked the brakes to see if they were stuck or hung up...no on either one ...all four wheels spin freely when truck is lifted....The Doctor

If it doesn't need it, it will eat a $400 hole in your pocket for nothing - that's what it'll hurt. The idea is to diagnose the damn thing - not rebuild it just to be sure the bases are covered.

Luignut

You '96 should have OBD-II on it. Have it scanned for fault codes which may provide a clue especially if it is misfiring. Many parts stores will do this free on the chance you will buy repair parts from them. If you do this, write down the exact code and description. Just because it may provide a particular code does not mean that part is the defect. It must be interpreted along with other symptoms if any.

As far as check outs to start, use a residue free electrical cleaner and clean the MAF sensor in the air intake. You may be able to get at it thru the intake tube. If not, it can be removed with a tamper resistant torx bit. You can buy a set of these at many parts store for under $10. Check inside your vacuum hose to the fuel pressure regulator for fuel. If there is fuel, the regulator is shot causing excess pressure. It still may be bad,s o a fuel pressure check is probably a good idea. The test guage kit is about $40. I am assuming you have kept the plugs, wires, cap and rotor maintained. If not, a good basic tuneup is in order.

After you clean the MAF, you should disconnect the battery for 10-15 minutes to clear the ECM. Restart the engine without touching anything. Let it idle for a few minutes and then move the selector thru all the positions for a few seconds each to allow the engine to relearn it's idle. Drive it around for a few miles to let it relearn it's operating parameters and see how it does.

A plugged fuel filter or weak pump can cause a loss of power but, they rarely cause a drastic drop in fuel mileage because the fuel pressure is reduced resulting in less fuel delivered.

As far as the converter is concerned, yes, it can cause a drop in power and fuel mileage. Usually a plugged converter will result in an unusual exhaust sound like the engine is is turning into a vacumm cleaner instead of having a normal engine exhaust sound. A good muffler shop can remove the O2 sensor and install a test guage to check for excessive backpressure. If you need a converter and intend to keep the trck for a long while, make sure they install a name brand converter or the OEM converter. Walker and Arvin are OEM suppliers with good products. The best route is the OEM if you are not sure of the product. MAny generic fitzall converters that use a single unit to replace 2 or 3 converters do not usually last very long if you must pass emissions inspection as we do here.

Theer are other things to be done before you spend megabucks on a converter that won't cost much to check out first.

Good luck Lugnut

...potentially again and again! My theory is that converters sometimes just die but more usually get killed by something upstream.

Absolutely. A fellow can throw parts at something like this for a long time without hitting the right one. Whoever suggested sticking a trouble code scanner into the On-Board Diagnostics II connector had the right idea -- combined with a good read of the shop manual. And it's a device that will be of ongoing usefulness.

Cheers,

--Joe

I'm getting it scanned Friday ...the check engine light does come on every so often (usually when doing 70 mph straight for more than 3 minutes) but does not stay on. Again, its only under certain conditions. I will check the brakes again, but I'm fairly certain that's not it...I will certainly post results after I have the codes read on Fri! The Doctor

It's not your brakes, if they were dragging that bad you'd have major smoke after 3 minutes of 70 mph. Bob

How many miles since you changed your spark plugs and other ignition parts?

Spark plugs & wires were changed this past summer, no other ignition parts were changed with that tune-up. The Doctor

Maybe now is the most common time of year for ignition problems. I remember replacing plugs, wires, cap, and coil on my '88 Sable one Halloween night. That fixed the won't-start problem. I would suspect the coil.