Bought a '96 Ford F250 with a 460 about two months back. Given it has a big block, have never been impressed with the acceleration. Had a coolant leak between the block and timing chain cover. Got that taken care of. Figured I would tune her up at the same time. Same problem still there. She idles just fine. She accretes just fine when not under a load (heavier acceleration).

I have done the following and am now looking for pointers on what to check next. Any assistance would be appreciated very much as I love the truck.

New plugs and wires
New distributor cap and rotor
New tensioner
New radiator
New PCV valve and the hose attached to it
New air filter and breather filter

Running some fuel injector cleaner through her right now. Will then change fuel filter.

There has been improvement with the rough idle she had (a lot better), but the original problem of rough/poor acceleration when I put some heel into it remains. She just seems to be holding back.

Advise anybody?

On another note, front fuel tank leaks through the cap as the day gets hotter. Only does it after I fill up. I realize fuel expands, but is there a vapor hose or something that might be disconnected causing this problem-or clogged? It's the front fuel tank only that has this problem. Is this common on this model Ford?


Thanks!

 

Check the timing, I bet it's not set right. Be aware you need to remove the spout plug when doing this to disable computer advance. Stock timing is 10deg BTDC but most motors will take 2-4 degrees more, try adding a couple degrees and then test under load listening for audible detonation(pinging), if you hear any back the timing off until it stops.

You also say you get fuel spilling out the front cap, does this happen when using the front or rear tank? If it's the rear you have the fuel transfer problem.

 

Hell, not sure on the fuel tank. I believe it was the front tank. Never encountered a fuel tank leaking out the cap like this. So is there a regulator between the two tanks?

Will check the timing. Not owned her all that long and just trying to get a tuneup done so I know what HAS been done (and when). I did have the timing chain cover off to replace the gasket that was leaking. Just wondering if I did anything when it was off-don't believe so as this symptom was there prior to my repairs.

 

Continue to have same issue of acceleration slow doing just fine. Under a load, it just sucks-sputters and loses power. Did adjust timing since last post...will change fuel filter next. Other suggestions welcome.

Thank you.

Russ

 

When you had the cover off did you replace the gears & chain , if not was there any slack in it ,???.....Lew

 

Here's a couple of ideas not mentioned to check out, hope you get her going good. How many miles on her?

fuel pump
ignition coil
faulty distributor, worn shaft
valves leaking
partial exhaust blockage
vacuum system not right
feedback system faulty

 

The truck is sitting at 102K miles. When the timing chain cover was off, did check the gears and chain...looked fine.

Will look into some of the other suggestions. The game plan is to start with the cheapest and work my way up. Ford dealer can throw it on a diagnostic and might help lead me in the right direction.

I will mention that adjusting the timing made a major improvement, not only in performance, but mileage for about four weeks. Fuel filter is next.

Faulty feedback system...not familiar with that one.

...and there was a vacuum leak, but got that repaired-check engine light has not come on since I repaired that.

 

I had an irritating hesitation/stumble/lack of power when under load at highway speeds that survived every remedy I threw at it (including a motor replacement). After some reading here, I solved it by rerouting all of my spark plug wires so they were as far away from each other as possible. Immediately fixed the issue and was free. I know its a different motor, but worth a shot and its free.

 

[quote=BigRedFordTruck;8894197]

feedback system...not familiar with that one.




sensor's

 

"Feedback system" mentioned is probably the EGR, best bet is to pull the codes to see if anything relavent is flagged and then proceed accordingly. If the EGR valve is not fully closing it could cause some of the issues you are describing, and simple carbon buildup could be the cause for that.