Hesitation/bucking-help?

[Summit]

BuCkInG wOeS

todd that pretty much sums it up with my truck. i'd ask how your performance is but your not stock. was your performance WAY down stock? mine sure is. i'm too embarassed to post on the mileage suvey, i drive almost a 1k miles a week, so it gets checked often,this past monday pocatello,ID to boise,ID empty cruise at 79, 11. 2mpg. last night towed my 26ft gooseneck & my 8000lb skidsteer from boise to pocatello on wet & snowy roads so speeds were from 35-65mph,7. 54mpg. just towing the gooseneck empty i have a hard time doing the speed limit. heck empty i lose speed at 75 with cruise on up 3-4%grade, my truck is just plain sackless. LATER

 

[Todd T]

well mine is far from being sackless. if fact it has a pair hanging off the hitch right now.



my mileage has been great. I keep track of every drop and to date my overall that 2250. 52 gallons run through i have averaged 19. 01MPG's my last 2 tanks were over 20MPG and that is hand calculated not the POS computer thingy.



I cant figure out what is doing this. it has to be the fuel management system. at first i always thought it was the drivetrain. but with the way it does it in 4WD that proved it out. there was enough drag on the system to keep it from slacking-up. which is what I thought is was doing.



then i thought, well it must be the VP44, but you said yours was relaced and it didnt fix it.



did they replace your APPS or crankshaft position sensor too?



its not the MAP sensor i replaced mine early on. its not the IAT sensor i cleaned mine. (even though it didnt need it)



I think the reason yours is so bad is you have taller tires and it lugs it more.



this really blows, doesnt it?

 

[Summit]

swung by the dump earlier with truck traier & skidsteer and was a little shocked when she handed me my scale slip, 24,420lb. thats pretty heavy but on flat ground i cant get over 50-55in 4th wot and it takes atleast a mile without a downhill & then flat i can carry 65 but thats it! we used to tow a b-hoe with a 98. 5 24v and could just criuse at 55mph & that wieghed alot more. skidsteer (8-9000lb) b-hoe (15-18000lb). LATER

 

[Todd T]

it is difinitly temperature sensitive. as the outside temps drop the problem gets more pronouced.



I thought about relocating my IAT sensor up into the main intake tube to see if it helps.



I have to get a new one and splice out the wire to make it longer. I'll let you know what it does if anything.

 

[Summit]

i did it anyway

took truck back to dealer even though its bucking & whatnot they said run it ,eventually it'll set a code? so i picked up my injectors today at bully-dog, supposed to be stage II but were out so they gave me a set of stage III for same price. well an hour later i was off in a cloud of smoke. only drove about 35mi tonight just cruising, Egt same, wot can get 1400*in 4th was to chicken to see how high it would go. what a HUGE power gain. i also added the boost elbow, now i get 23lbs boost. unfortunatly still somthing amiss though, in nuetral, if i bring rpms up slowly at about 1600 rpm engine starts to run "rough" like somethings out of balance,not a solid "skip". get to 17-1800 &just keep it there it starts the "surging" say, 100 rpm surge. get to 2000 & beyond it clears up. its drivin me nuts. i even ran some #'s at dealer today for 02 6-speed but to much $$$ for now. LATER

 

[PROSTAR190]

Has anyone had any luck finding the cause of the problem??? I am seeing more and more posts claiming the same problem. This condition will drive you crazy.

 

[Summit]

still st,st,st,studdering

i haven't fixed mine yet, i wanted to fix before i bombed, but bombing magnify's the problem so i figure it might help set a code or something ( i know who am i kidding?). should have my truck back tomorrow and mech wants to check for air in the fuel line, says that there's some plastic pick-up line inside another in the tank that can cause lift pump to "suck" air if the plastic breaks which would make it run like crap.



i am working hard with my tech. to figure this one out if i get mine fixed i'll be sure to post it. my tech thinks the air in line is a good idea since it's been going on three months without a code, and he's seen several that have been bad.





other than that it's like there's a sensor on all these truck's that's got a "malfunction" that doesn't set a code, some people think it's like a light bulb, it works or it don't , but i've seen light bulbs that "flicker" for a long time without burning out.



any one else ??? LATER





i hate the thought of playing the sensor changing game as it'll add up fast since my outfit is out of warranty

 

[Big P]

I'm experiencing this problem too. It showed up after the BD PNP2 was put on. It was an occational problem until I hooked up the truck to tow 3 snowmobiles through the hills of Vermont. With the cruise on the problem mostly occured at around 15lbs. of boost. On the way home I took the box off and it never hesitated or bucked once. It has to be the programing of the box. It seems that we all have either a VA, BD, or EZ in common, with no pusher pump set-ups. Does anybody have a fuel pressure gauge on their trucks? Mine is going in soon.

 

[rubberneck]

i got a gauge

Yep, i got a fuel pressure gauge, and my lift pump appears to be ok. notice i said ok but not great 12 psi idle, 2 psi at wot with ez and dd3s. depending on who you talk to this pressure may or may not be good enough. but that is for another thread. I will be adding a pusher pump just to find out however, as this thing is driving me nuts. the reason i do not think it is the fuel press, is that my truck does not buck at wot only moderate throttle, and fuel press is usually in the 6-8 psi range when it is doing it. The ez or the va is not the answer at least not in my case. my truck will do it with nothing on it. It is much worse with the dd3's. and the ez, however it appears the problems we are having is in the truck somewhere, and adding power just enhances the problem. i took my truck to the dealer wed, and they reflashed it. I need to either hook the trailer up or put the dd3's back in to see if it fixed the proble ( im not holding my breath) if still there, i will leave the dd3's in and take tech for a drive so he can feel it. I am really leaning toward the pump, or a sensor going out, but not bad enough to set a code. my truck was perfect for the first 9000 miles, and then this started,and is getting worse. so, something is on its way out. who knows maybe ill get lucky, and whatever it is will just go (. ) (. ) up and set a code. then the tech will have something solid to work with. (i wont hold my breath)

 

[rubberneck]

I might add, that power on my truck is as good as it has ever been, and as a matter of fact if you are hot rodding around, you wouldn't even know there was a problem, its when you are cruising and just ease down on the pedal to pass etc that you start jejejejerking around

 

[WCrovo]

Mine has done the hesitation/stumble thing 2 or 3 times. At first I atributited to my Pacbrake. Then it did it yesterday and my Pac was not engaged. Mine dose it after it has been idleing awhile as in a bank line or waiting to get into traffic. One hesitation then it goes and has no more running issues, Gets great fuel milage and has all the nuts in the world. Gonna hook up a pressure gauge I guess and ck the pre pump.

 

[jwhite1]

24 valve engine

I have a 2001 3500 with 3. 54 gears and 5 speed. At rpms less than 1200 it delivers power very roughly, but once it gets above that, it has a lot of power. Also it has a Power Puck on it, which made no difference to it before installation or afterwards. It did, however, improve fuel milage about 2mpg, plus gave me the added power I wanted. By what I hear from others, this is a common problem that needs to be fixed for the benefit of all of us who need our trucks to pull heavy loads. The truck has 14000 miles on it and has been doing this since day 1. I also have 2 other 2500 trucks with 12 valve engines and really love them both. They each have over 100,000 miles and run great. I hope someone can help us with this problem for an otherwise great engine. Thank you. :confused

 

[Big P]

I hear what you guys are saying. Like Rubberneck said I wish something would just break so we could figure out what it is.

 

[JMarkos]

Well mine seems to be getting worse, everytime I pull it does it more often. I had to pull aginst a head wind yesterday morning for about 25 miles, that was a long 25 miles. For me also I am ready for whatever it is to just break. Off to the dealer on friday, hopefully he can find something, he says it doesn't sound too serious, ya ok.

 

[Summit]

its getting worse

on the way home today my truck was bucking as usual so i tried to keep it doing it and after 1/4mi it started cutting out and pushing it to the floor didnt help this time as usually i can push peddle past the bucking. now it dies for 3-4sec. , run for 3-4sec. , on for 3, off for 3, on for 3, it'll keep doing it until i let off the throttle. all the guages were working fine, only the fuel was surging with the stall. as soon as truck would die (6psi) guage would jump up to 11psi and back to 6psi and back to 11psi as it was stalling. i called my tech and he said a 3-4sec stall isnt long enough to set a code(it didn't) anybody else with similar?? input??

 

[JMarkos]

Mine isn't that bad yet but it would sometimes seem to not want to clean out even at WOT. I just talked to a buddy of mine that works for the transit authority, I think the buses have the 8. 3 but when I told him what was going on the first thing he asked was if I had ever had my valves adjusted, he said he has seen the same thing with the buses and a valve adjustment cured it. Has anyone tryed that? I just got done giving mine a nice bath, wax and detail, maybe it was just ****** it was so dirty, LOL.





Everyone have a Merry Christmas.





Jeff

 

[Big P]

Summit's gauge is telling him that it is not a fuel delivery problem. Maybe the problem is not the vp44 at all, atleast not mechanicaly. Could it be faulty signals the ecm is providing the injection pump and it's amplified by the more aggressive timing a performance box gives? It's almost like the vp44 is confused and doesn't know where and when to pump fuel when this happens. Just a thought. Merry Christmas.

 

[JTroiano]

I've heard people talk about a duty cycled vavle that lets the fuel into the pump and it regulates the time and amount of fuel to each cylinder. It seems like a lot of work for one injector? A EFI car has one per cylinder and they still mess up. I wonder if the valve in the VP44 is sticking or like people are saying there is a bad connection or and interupted signal. I could have sworn my truck has stumbled a couple of times and it only has about 7,000 miles. Maybe I'm just parinoid. (sp?)

Jon

 

[tmacc]

BTW Folks FWIW, Those of us w/ 4. 10s also have this problem. I've had it since the #18-024-00 (trans) reflash in Feb. Took it back in March complaining about the shudder. They did the same reflash which did nothing. The truck was bone stock at this time. Warm weather came and it seemed to go away or just not as noticable. W/ a few mods it does acerbate the problem. Hope we find out soon what the problem is.

 

[jwhite1]

rough running 24 valve

My '01 3500 24 valve engine seems not to be the only one with this rough power delivery at low rpms say about 1200 or less. Maybe these guys have the right idea about mixed signals from the ecm or maybe a weak supply pump, but whatever it is, it has done this since day one, and is no better or no worse. It is just plain annoying to drive a bucking engine. You would think that since we have all this fancy electronic technology that something like this would never be allowed to happen to a fine engine like a Cummins. The 12 valve engines I have are genuine jewels and I really love them, but this 24 valve engine is a disappointment in this respect. Also I have a power puck on it which gave me the added power I needed, and it pulls really great at rpms above 1200. I have talked to other Diesel technicians and they don't have a clue. I think personally that it is mixed information from the computers to the pump, but what to do about it, I don't know. I'm thinking about trying to add an additional supply pump in series with the existing one to perhaps help insure ample pressure and volume to the vp44, which probably needs all the help it can get. Anybody with a fix, please lets share it. Thanks, Jerry PS I think everyone needs help on this one.