Hey Guys, I am fresh to the site - have dug around on some of the tests that can be provided, did those and after running thru that and replacing the MAP sensor we are still at a loss so I am reaching out to you guys for some help if you would....The truck is a 2001 Dually, 3500 4x4, has the HO engine in it with about 83,000 miles on it. Fuel system has a Raptor 150 Pump with a Draw straw and bigger lines to support more fuel not only to the filter, but past it and direct to the VP. I run a pressure gauge that reads pressure just previous to the VP to monitor the pressure right before the VP to keep an eye on lift pump pressure and filter condition. It's been holding steady at 19 pounds while truckin' down the road. When fueling, I use Wallyworld 2 Stroke TC3w Oil to keep the VP lubed at 1oz to one gallon of diesel.Here is what has been happening:Acts like dead pedal once in a bit, won't get out of it's own way sometimes and even floored truck will not accelerate hardly at all - will exhibit lean smoke at the top of the rpms while trying to get 'er moving to the next gear. Then after some time, it just jumps back into life and away we go - sometimes it runs like there is no issue and sometimes it takes a while - this is both warmed up and cold. Turbo response during this "episode" is basically gone. Even when things are operational, the EGT's seem higher than they used to be. One second it's running like its new, the next, it won't get out of it's own way. Sometimes when I start out in second (it's a 6 spd manual) it wants to almost stall and that is when I know that things are not starting out so well... The problem is random like I said - you can have it floored and there is no response and then 4 seconds later - hey!, it's alive!We've reset the apps and on the OBII Snap On test, it's reading %'s as far as foot pedal movement-We are attempting on getting to the root of the problem and I have two quick questions before I give you the War and Peace size story that backs the history on this-1 - On a VP44 Inj Pump, can it "come and go" timimg wise to advance great one round and then not the next?I guess in other words, can the non-response be caused by a pump that is failing advance-wise and then the pump get back into time and it'll run fine? 2- On the MAP Voltage Low test, the MAPS did not seem up to par voltage wise on the OBDII Snap On test so I replaced it - here is the question:The Maps that I took off the engine is twice the size of the one that was sold to me, inlet hole is for pressure reading is half the size as well - It was however the harder one to find and about $166 my cost - it does have the right plug in for the harness three-pin oval, not the round plug in - part number on the new one is EC1854 made by BWD - the stock Mopar one has a 10702 on one side (i think that is a 2 on the end) and a 3417030 on the other. That seem right that they are different sizes? I can't find anywhere that has the bigger one....? it took a socket that was an 1" 1/4 to get it out and the new one took an 1" 1/16....Doesn't seem right?That is a place to start as I don't want this to be 7 pages long to start with as I know that you have things to do other than read a novel from me...Thanks for the help - I'll have more as we go and please feel free to ask questions as I am sure more info is helpful.Thanks all, have a great Sunday!!

Are there any codes present? These are common symptoms of a bad apps or dieing vp44. Look here for cheaper map and all most other sensors. http://www.genosgarage.com/searchprods.asp

Ryan has you started in the right direction. Need to check for codes. You say you have 19 psi going down the road. What is your pressure at WOT? What is your pressure at idle? Do you notice a drop in pressure at any time when you are driving? When was the last time you changed your fuel filter? What procedure did you use to reset the APPS?

Bri,Welcome to the site!!Sounds like you are heading down the correct path. Sorry I can't help you on the MAP. From an engineering standpoint, as long as the voltage output table relative to intake pressure is the same, the physical shape, size, brand shouldn't make a difference at all. The vp can have no codes (it doesn't know that it has a problem) and still have problems. My brother's 01 is a perfect example. You need to eliminate the APPS as a problem and the lift pump. If these are rock solid, and you still have dead pedal, it is the VP. My brother has noticed that his is temperature related mainly. If the truck is cold, he has dead pedal almost constantly, when the truck is warmed up or warm weather, the problem almost does not exist. The VP is not really dead, just cold solder joints on the circuit board. If you THINK the apps could be part of the problem, get an app from Timbo. Give him a call. (super nice fellow. Will bend over backwards to help you!!!) He will try to talk you out of buying one after a couple tests (assuming yours passes those tests.) GL HTHHag

Everyone knows there is 2 thing cause dead pedal...1. APPS Sensor failed (P0121, P0122, or P0123)2. VP44 with or without codes.Now there is a 3rd thing to the list...3. ECM.I've now seen 2 cases of ECM's giving dead pedal...

Hello and welcome. A good whle before my ECM crapped out I had a similar problem. It was like something was turning my Ottomind tuner on and off. I would be cruising just fine and like flipping a switch I would loose power. Not to the degree you are speaking of. I just seemed to loose the power the tuner was providing. It was intermittant and I never figured it out. Then the ECM went. After replacing it I have never had the problem again. I also was experiencing dead pedal and bucking issues. That turned out to be low fuel pressure issues.I am not trying to say rush out and buy one, they are way to pricey just to throw at it. If you know someone that has a truck like yours maybe they would let you use theirs and see if makes a differance.I believe I have read where the newer MAP sensors are differant from the oe. I dont know for sure.

I agree, my new map was a different looking unit than OE