I don't know if my truck has some sort of adaptive learning with the throttle response, because I don't remember the truck always doing this. I know the newer mustangs have it. but with my truck it seems like the throttle is pretty unpredictable. I realize the nature of a diesel in that it naturally wants to have a lag then take off, but with my truck sometimes it almost to the point of nearly breaking the tires loose. say I need to use half throttle to speed up a little faster than I normally would say I am making a right turn on a busy street cars are coming and I need to speed up a bit faster than usual, I get the truck turned and goodness sakes it about snaps my neck back and I am left thinking I didn't mean to do that. I mean the acceleration really hits hard. some would say this is a good thing, the problem is sometimes I don't want all on 100% power, it just seems more difficult to control the power than pretty much any vehicle I have ever driven.

 

I am not sure what to make out of the things we are seeing. On the other thread about lagging throttles, it appears something is preventing quick accelaration at start up and then there is what you are seeing (me too BTW). To be honest, I haven't looked under the hood to see if this throttle system is fly by wire or mechanical.

I have adjusted my driving style a bit realizing that these things are happening.

 

1. Fly by wire.

Been that way for all Ford products in North America for quite some time.

2. The issue smacks of low cetane.

Have you tried a bottle of cetane boost?

 

Been bathing in the stuff. Power Service Cetane Booster with anti gel. It almost feels like the days when my automatic transmission was slipping.

 

I remember when I bought my first diesel, It was a 7.3L and when I took the truck for the delivery test ride, I gently pushed the throttle like I would have in my gas engined truck. It didn't go, Salesman sitting in the front with me said, Mash it, Which I soon learned to do.

When I bought my 2003 6.0L I quickly learned that it also had some lag and then it ran like a raped ape when the turbo got spooled up. So I had to learn how to floor it and then feather it as the turbo came up to full pressure. In fact some days at busy intersections, I almost needed to power brake while I feed some fuel to get the turbo working so I could launch into busy traffic so I didn't have that first little bog trying to move off the line.

I'm sure your 6.7L isn't a whole lot different. Diesel engine need a turbo to get full power. Turbos take a moment to spool up and creat pressure. the new design of the 6.7L is supposed to help get that done quicker, providing less hesitation. For the most part, this new engine is much better about getting the truck moving from a dead stop. Most of the time I can with just a light throttle putt putt away from an intersection. I did notice yesterday, I was running late, traffic was heavy and I didn't want to wait for another opening, I decided to shoot through a gap in traffic. I jumped on it much harder than my normal day to day driving and was surprised at the rear chirping.

My advice is that you will learn to feather the fuel appropriately with usage, You will slip up once in while because conditions change.

Cowboy, If you are getting poor cetane ratings in your fuel, take a look at Opti-Lube from down in Utah county. They make a great diesel fuel improver. It was rated one of the highest for adding Lubricity to Ultra Low Sulfur diesel, And it's local to boot.

 

Take a look at a thread related to throttle on Regen...

See if the symptoms are similar.

 

Every Ford diesel from the first generation 1995 7.3L PowerStroke have had electronic throttle control.

I've noticed lots of lag when taking off when the engine is cold, and I think this is a protective feature in the programming to protect the engine from high power output before the engine warms up a bit.

My 6.4L did the same thing, I think it's a characteristic of modern electronically controlled turbodiesels.

 

There are two issues:

When you spray in cold fuel to a cold combustion chamber, if there is not enough heat there, it will not ignite --- it is easier to ignite a smaller charge than it is a larger charge.

The rest (unignited fuel) just goes down the tailpipe and make EPA see green.

Hence the white smoke when you start up real cold on the pre-SCR / DOC models.

There is a electronic (read software) limit on how much fuel is injected (mindful that it would not only not combust, but in excess amounts, bog the motor.

As it warms up, the ability of the engine to "eat" rises... and it is gradually eased up.

Whereas a gasser can technically go nearly WOT cold, a diesel really don't like that.

Oh.. cold fuel that do not combust also coats the cylinder bore and end up in oil.

 

This makes lots of sense. When cold the truck will make power if pushed, but it prefers to take it easy until it comes up to temp.

Knowing how harsh it is on the engine to make lots of power cold I like to baby it, but I've made the mistake of pulling out in front of people before...it will move when it has to. Lots of white smoke though.

 

The related debate is that idling in very cold climates is actually not as bad as the alternative of starting up from extreme cold (e.g. -30 -40) as long as the oil is changed on the severe schedule.

Ford got out of recommending long idles because of carbon build issues with bad fuel, and also under EPA / Greenies pressure.

Go anywhere in the deep freeze zone (e.g. north slope of alaska), and you will see vehicles that are either garaged in heated space, or just never turned off.

Cost of doing business there...

 

Being my first diesel, this makes a lot of sense. I have driven turbo boosted cars before, but you are dealing with a lot less mass to get moving.

 

They are and they aren't. I am using the cetane booster and at the higher level they are recommending to increase cetane. Even on warm days, like today on the east coast, it still is doing the same. Unless the cetane in the fuel I am buying is really low, I am not sure it is a cetane issue. Painted's explanation makes a lot of sense to me.

 

I think that explaination works for the cold running issues. When it is warmed up, there still is the same type of lag. I am thinking that Painted is on to the real culprit. Turbo lag. I would like to see the specs on how many inches of compression it produces over a zero to top speed range. They don't use waste gates on these, do they?

 

If it is bogging only when cold, Painted is probably right.

Diesels are not intended to work well from cold until it warms.

If the bogging happens at operating temp.. something else is going on.

If you used cetane boost, it will up its number about 5

That is, from 40 (US average) to 45.

Should be in the "good" range.

 

I have an f450. I note that it is touchy off idle. It will break the tires loose going around corners when it slippery on the 1-2 and 2-3 shifts. In my opinion, this is because of the stiff gear ratio (4.30) and because ford has programmed the throttle response to be very heavily weighted to the front end of the accelerator I.e. To utilize the fast spooling characteristic of the new turbo they dump in a lot of fuel with minimal pedal application. The effect is to make your vehicle feel much more powerful than it really is. So I find that on the highway if I step on it an inch it goes like h*ll but if you stomp it down it doesn't go much better. Much like a Harley with a large throttle body the percentage increase in airflow is greatest at the beginning of travel of the TB butterfly. Being electronic, the engineers can program in whatever response characteristic they wish for a diesel. By magazine report on a test of the early duramax trucks Chevrolet chose the opposite strategy of putting the power at the end of the accelerator pedal travel.