have you checked the intercooler boots for leaks?? if your smoking more then normal and having a power lost, you may have a slight leak from the boots. just a thought.

 

Opposite issue...no smoke at all under WOT...

 

I'm under the assumption here that you have a fuel pressure guage on this truck that you can see all the time. If not you need one ASAP. The most important thing you can have on these 2nd Gen trucks after tires. Even if the truck is not modded you may have gotten even more miles out of that stock VP if you had a guage. Guess I should also ask if you change the Lift Pump or at least checked it when you changed the VP. More often then not the reason the VP dies is because he LP goes bad and takes out the VP. If your LP is still bad you may be killin your replacement VP right now.

 

The VP44 never died...we had it replaced along with injectors as preventative maintenance. We figured the injectors and the VP44 were both worn, and replacing just one would cause extra strain on the other causing other issues.

This isn't my first go around with a VP44-equipped truck, just the first one exhibiting lower-than-normal power output.

The lift pump has been replaced several times, the last time being less than 20k miles ago.

And while we don't have a fuel pressure gauge, we have a low pressure warning light set at 7psi. It never illuminates except at start up. It does NOT illuminate under WOT or load, which would be when the truck is demanding the most fuel. And they do work as a "gauge", just you don't have a number other than more than 7psi or less than 7psi.

I know the fuel system is fine, just seems like its not getting "told" by the ECM to add more fuel...

 

Just checkin, but ya that APPS adjustment made a significant improvement in mine.

 

If its the stock style lift pump, get rid of it and get an airdog or fass. I went through four factory pumps in one month on my completely stock 98.5 24 valve before i switched to the fass, since then, its running great and i havent had to replace the pumps. also, this may seem dumb, but have you checked your fuel filters?? sometimes overlooked and they can cause great problems. id also look into reflashing the the ECM(if the IAT and MAP sensor swap/cleaning dont help it first) Motorolla made the damn things and it seems that from 98 to 2001, some trucks had some ECM issues, i know there was a recall on them on in may of 98 and again in early 00, you just had to take it to the dealer and they would reflash it and go.

 

From the first post: "Filters have been replaced within the last 6k." This condition predates multiple filter changes...

The factory pump is fine on a stock truck, if its not pulling down then it is fine. This makes the second VP44 (my 99) that we've got more than 200k on, and it also ran nothing but OE lift pumps. If it was the lift pump, we'd see it under WOT as the low pressure light would illuminate as the demand of the VP44 exceeded the supply capability of the lift pump...we do not see this.

 

Boy if it was my truck, I'd throw new IAT and MAP sensors in it with out a doubt.

 

i seen that, what i meant was since the problem started. I once last winter got a bad tank of diesel and it ruint my brand new filter, clogged it completely up. i dont know man, maybe some how the APPS sensor is messed up but not throwing a code or maybe you have a slight leak in the headgasket thats not allowing it to leak coolant outside the motor, but enough of one to lose some compression.

 

Filters have been changed several times...

The truck runs like a champ once I get it in the wind, it'll pull a moderate hill from 60 to 105 mph in no time flat (I was chasing a BMW), but at lower speeds and RPMs it is a complete dog. Someone made the comment about my owning a 04.5 600CTD might be clouding my judgment, but this truck is every bit as fast and strong as my 04.5 once its up to speed and RPM. Is fun to drive if you run it hard...but just tripping around its very sluggish...

We would see a leaking head gasket through the coolant reservoir correct?? It should force air out of the system and cause the coolant reservoir to bubble? There's no blowby from the blowby tube to speak of...maybe I'll grab a UOA and see what that tells me...