I was driving from Salt Lake City to Gillette WY (about 550 miles) and at the half way point when I floored it to pass a Semi my truck downshifted but stuttered at around 3500 rpm. It would go no higher. I pulled over, put it in nuetral and slowly reved it up to 5500. But when I floored it, it started to stutter again. I changed my fuel filter this past summer so that shouldn't be the problem. Any ideas? Thanks

 

For the price of a filter its probably worth changing it out again...

 

air filter could do it-also try cleaning the MAF (mass airflow sensor)

 

a bad coil on plug tends to show up under heavy load -

 

I'd scan the truck for DTCs. It is probably a missfire and may possibly throw a code.

When the last time your plugs were changed?

The fuel filter should be changed every 10,000 miles. The V10 goes through quite a bit of fuel. Clean the MAF every year.

 

It'll probably NEVER throw a code for a misfire:

https://www.ford-trucks.com/forums/5...t-come-on.html

 

Sounds like symptoms of a bad TPS.

 

I'll 2nd that one.

 

My boat does the same thing when the plug wires are going bad.

I would replace the COP boots first and see if that fixes the problem. Its cheap and easy to do.

 

This is what confuses me. It seems to only do after it has been driven for over a couple of hours. When I left Denver yesterday morning everything was fine. Once I got home (7 hours later) I floored it to pass somebody and the engine began to stutter again around 3500 RPM. I think I might have to buy a programmer after all and see if any codes come up.

 

Wow! 6 different suggestions!

Obviously the problem is a heat related problem since it only does it once the engine has been running awhile and the offending part has been working.

That rules out the fuel & air filters. Doubt it's the MAF.

Most certainly spark related.

 

Could very well be bad fuel pump. Lots of times they act up once run for a while. That would cause it to run fine at lower rpms, but then have a very lean mixture at wot. You could throw a fuel pressure gage on it and see if you can get it to act up while watching the gage. intermittent problems are a bear.

 

Now that you mention it, it does seem like it is running lean in that condition. But then why would it rev up to 5000 rpm on the side of the road in Nuetral but not in gear on the Highway? Maybe because there is no load on the engine?

 

If the fuel pump actually is the problem, yes it requires much less fuel to rev the motor than to move the truck. Doesn't guarantee that's the problem, but it seems to fit.

 

That's makes sense to me. Do our trucks have a pump in the fuel tank as well as on the frame rail?