I have a 1996 F-250 super cab with the 351 engine with 123K miles. about 1 year ago I started to notice a loss in power. about 9 months ago my fuel milage dropped 4 to 5 miles putting me at 9 or 10 miles a gallon. I replaced the fuel pressure regulator because it had gone bad according to a good friend who has his own shop (he tested it and found it to be bad). My father inlaw said that he thought that by removing the cat converter i would gain my power back so I gutted the cat. I did not get any gain in milage or power. now several months later I am at a loss and so is everybody else. At low RPM the engine bucks and jumps at high RPM the engine bucks and jumps. In 5th gear (standard transmission) it bucks going down the interstate. No power what so ever. It back fires something fierce every once in a while. I use the truck as my main transportation to from work (not far) and I hall a goose neck live stock trailer once in a while. I'm scaried to hall the trailer now. I have checked the timing by turning the crank and watching the distributor. I get about 1/2 an inch of movement before the distributor moves. I maybe able to answer other questions if needed to help with a solution. The truck does burn oil, but it has done this for about four years and gets worse. I can see blue smoke when parked and running. I have inspected wires and such. I see nothing that would regulate and replacement.

 

What exactly do you mean by "1/2 an inch of movement"? You should get an immediate movement inside the distributor when you rotate the crank. How old is your timing chain & set?

I don't know if they still make them this way, but years ago Ford used plastic teeth on the camshaft timing gears. When the plastic got old and brittle the teeth would crack and fall off, and when you'd lose enought teeth your timing chain would jump. I've seen it many, many times, and the symptoms you describe sound eerily similar....

When was the last time the timing was checked, not with a light but by verifying TDC on the #1 cylinder? You may want to start there, especially given your "1/2 of movement" thing.

Good luck!

Jim

 

1/2" of movement with a rachet wrench. measuring the half inch with the end of the wrech movement. I have never had the timing checked and everything about the engine is original. except for the pluygs wires distributor that kind of normal replacment stuff. Heck believe it or not the battery is original.

 

I had the samething happen in my 87 250 reg cab 4x4 and i ended up pullin the 351w and putting in a 302 and i runs fine now. Hate to bring bad news but you might have to do that for yours. If you do i aslo have a 351m crate motor that wouldnt work in mine for sale if you need it . Just trying to help and not bring bad news

 

Ok, 1/2" of movement at the end of a ratchet wrench or breaker bar could easily be caused by just the flex of the bar or play in the socket. I guess I wouldn't worry too much about that. BUT, what happens when you crank the wrench the other way- then how much slack have you got? IOW, how much movement do you have between turning CW (tighten) and CCW (loosen)? That should give you some idea about the condition of your timing chain.

However, it still sounds ignition related to me- you talked about backfiring and such ("bucks and jumps"). I'm no expert, and I could be way off here, but that's where I would start. 123,000 miles on the original timing set, distributor, and all that. Heck, your distributor could be just worn out. Maybe pull it out to see if the bushings are shot.

 

I'd replace the plug wires first thing, changing the cap and rotor at the same time is a good idea. Not a lot of money could gain good results. Good luck.

 

Has this triggered the check engine light?

I would second the timing-chain as a possible culprit, and throw in a worn camshaft as a second one.

 

Clock wise and counter clock wise both yield the same result, 1/2 inch movement before the rotor moves.The distibutor cap, button wires and plugs are no more than a year old and maybe 8k miles on them and appear at this time to be in good condition. Any others suggestion out there. I will see what I can do to check that camshaft. does anybody have any questions for me that may help narrow the problem. Thanks for the responses. Oh yeah the light has not come on. The computer was read sometime ago at the first sign of problems. It only gave a fuel pressure reg code.