Hesitation/bucking-help?

[Summit]

tryed a VAchip other day liked power but picked up a bucking btween1000-1300rpm's,tried PE_EZ no problems . now a week later truck started hesitating or stumbling on take off today. then if i dont keep rpm's up it starts bucking pretty bad below 1400rpm's,i was low on fuel so i filled up different place-same problem,any sugg. appreciated.

 

[bipit]

if you keep the rpm's between 1000-1300 does it continue, if so look at your egt's. It could be a fuel/timing problem. Check your fuel filter for water. You said the EZ gave you no problems, but the VA did, Not familar with the VA, is there a provision for timimg advance, if not that could be your problem, and should so on the EGT gage, depending on how fast the thermocouple transmits the signal to the guage. Just a few suggestions, I hope they help

 

[Summit]

Originally posted by bipit

if you ifkeep the rpm's between 1000-1300 does it continue, if so look at your egt's. It could be a fuel/timing problem. Check your fuel filter for water. You said the EZ gave you no problems, but the VA did, Not familar with the VA, is there a provision for timimg advance, if not that could be your problem, and should so on the EGT gage, depending on how fast the thermocouple transmits the signal to the guage. Just a few suggestions, I hope they help

yes-continues let-out clutch in 2nd,or 3rd,its like it stalls briefly. bad TPS?

 

[bipit]

Originally posted by Summit

yes-continues let-out clutch in 2nd,or 3rd,its like it stalls briefly. bad TPS?

It could be a TPS. But I have a couple more questions, and some things you could check, before your take your truck to the dealer.



1. Does it hesitate when the EZ is unpluged.

2. Have you checked the EZ plugs to make sure they are seated Compleatly.

3. What kind of air filter do you have, if it's a K&N, pull the inlet hose off your turbo, look for oil on the vanes.

4. If oil is present on turbo vanes, clean your MAP sensor!



There have been quite a few people with similar indications, so I hope we as a whole, we can figure this out.



If these things you check, turn out negative. We will keep trying until we figure it out, I am a Master Diesel Mechanic, but all the engines I work on are putting out Between 1000 and 10,000 HP and weigh about 10-20 tons, and have zero eletronics.

 

[TurboDog]

Summit,

Have you checked your fuel pressure? Sounds like it might be a bad lift pump. From what I hear, the VA will make it do that if the lift pump is bad.

 

[bipit]

Originally posted by TurboDog

Summit,

Have you checked your fuel pressure? Sounds like it might be a bad lift pump. From what I hear, the VA will make it do that if the lift pump is bad.

TurboDog has a point, the lift pumps on these trucks dont have a good track history. I have 27,000 on my 3500 and I have been lucky so far. I have noticed that alot of members are monitoring their fuel pressure just for that reason.



Dont forget to check some of the other things though, start simple and work up. Make one adjustment or check then evaluate, if not you wont be sure just what the problem was.

 

[DennyDay]

Stumble

Had the same problem with mine, but with new lift pump -- e-mail BRoth or Matt at BD for suggestions. -- email address removed --



Denny

 

[Summit]

turned on my key this morning-wait to start (30*out) lift pump sounded like it was "gurgling" -ran for about 15sec. to pressure up? just had it replaced 3200mi ago,whats with all the bad lift pumps?? need to add fuel pressure guage. have many members had prob with TPS. truck always acts moody runs good-bad-good-bad,somone sugg bad TPS how much for one? oh i ended up not purchasing a "box"yet till i figure this out,thanx for the help. off to dealer this morning to check fuel pressue first,

 

[Summit]

went to dealer in boise area today,they were "too busy" to have there tech take literally 5-min to check lift pump!!!!! what a JOKE said to make app and they would need at least 2hrs to diagnose,thats not the kind of service i get in east ID i just happened to be there when my truck acted up & i sure as #@$! wont go back there. 5-star NOT!!! oh-there price for IAT $27 TPS $409(ouch). SORRY JUST NEEDED TO VENT. anyways i didnt get my pump checked but i notice that in nuetral if i bring rpm''s up to 1000 engine runs really rough but clears past 1100 hope figure-out soon want to start upgrades.

 

[TurboDog]

Latest findings????

Summit,

Have you got an update for us? How was the fuel pressure? If you get tired of the dealer, get you a fuel pressure gauge kit from BD. Mine was about $45. 00 and easy to install.

 

[Summit]

Re: Latest findings????

Originally posted by TurboDog

Summit,

Have you got an update for us? How was the fuel pressure? If you get tired of the dealer, get you a fuel pressure gauge kit from BD. Mine was about $45. 00 and easy to install.

actually i didnt make it to "my" dealer yet, with the holidays & all plus my diesel tech went to denver for 10 days,he'll be back on monday but i had to be back in boise in the a. m. what a pain working on the other side of the state. if i get time this week ill go to place i bought guages over here & add a fuel guage. ill let you know as soon as i get it figured. i sure wish RAPID RICK would check in and let me know if he's fixed with TPS as he had the EXCACT same problem. LATER

 

[TurboDog]

TPS

Thanks, let me know if Rapid Rick gets back to you about the TPS.

 

[Todd T]

hope you get it fixed, my truck has done that since it was new.



as in, still wet behind the ears and the hood never popped yet, new.



all I can do is let off, or floor it & power past it. any boxes or mods you put on, just amplify it.



I think it is the motor mounts. or something along that line.



does anyone know if they changed mounts on the 24v'ers and when, if they did.

 

[DLebedeff]

I'm having the same problem with my truck and I just got it back from the dealer last week. I've taken it to them 3 times now and they tell me that there is nothing wrong and to just take it out of OD when I reach 45 to 55 mph. OHH and the low temp is not an issue here in sunny Southern California. I only have 24,000 miles on my truck and I strarted notice this at 10,000 miles.



Dave













2001 2500 24 valve Auto 4x4,loaded SLT,Quad Cab longbed

 

[Runaway]

Same symptoms, no solutions!

As with alot of us, I have been getting more and more of the hesitation ordeal. I will be servicing truck this week some time, oil/filter change, fuel filter, etc, etc. I'm hoping for a plugged filter again, but I'm guessing it's elsewhere. I did the key cycle (3x) to see if any codes have been stored, NONE! Being an intermittent problem, beginning to think maybe a loose connection somewhere, but unsure where to start to look for an electrical plug not seated properly or... ideas?

 

[joel]

mine did that and it turned out to be...

not the lift pump but the injection pump. Went at somewhere around 45K and my dealer replaced it under warranty with no dramatics at all. Then again, I have a good dealer. I took it in and said I'm pretty sure the lift pump has failed (which they said would have also been covered at that mileage). They ran some tests, found normal lift pump pressure and investigated farther and found the injection pump code had been tripped. Ordered a new one and voila. Nice smooth running truck.

 

[Summit]

but its brand new

joel, within the last 3kmi dealer replaced lift pump(was bad), injector pump, injectors, turbo, re-flash, its only gotten worse since then add a chip & it makes it much worse-basically un driveable so i didnt puchase chip, bought injectors instead but from what i read on here injectors will "amplify" the prob also. so no bombing till its fixed. LATER

 

[Diese1nut]

Never ending saga.

After six trips to four different dealers with some repairs but no success on the hesitation, I checked for a code by using the key method. It came up P 1693 which says a "fault has been generated in the companion ECM".

I called another dealer and told them my history and what I had found for a code. They told me that those codes mean nothing to them and they don't even look at them. They said bring it in and we will have a look.

I'm not interested in dealers waisting my time. All I ask is hook up the scan tool and lets go for a ride. But no they just want you to leave the truck so they can park it out back and go have coffee.

 

[Summit]

why so many?

there sure is ALOT of people with bad lift pumps and hesitation problems, i sure hope DC & cummins is looking in to it. if i find something i'll be sure to post it. LATER

 

[Todd T]

summit, help me to understand what the truck is doing.



my truck, at those RPM's will BUCK. back and forth. the easiest way to trigger it is from a coast, try to speed up just a little. that will get it started and it wont stop. sometimes I can just let off and ease back onto the throttle real slow it will then speed up without doing it. other times after two or three tries, i have to just let off and then floor it to speed up past it.



it is not anywhere in the fuel system before the VP44. I have replaced or improved flow to all of it. my fuel pressure is rock steady at "Mrs Schreader valve" (Briar Hopper, you gotta love him) on the VP44.



if i put the truck into 4WD it is REAL BAD. all the way to 2000rpm's



I can still feel it in the upper RPM's just not as bad. it feels like the wind is gusting head-on, or kinda feels like the truck bounces up and down a little. weard description, I know, but that is how it feels.



even under moderately hard acceleration you can feel the truck surging, its not smooth.



again, my truck has been this way even before I added the injectors and PM3. they just amplified it. before those were on, i could just feel the surging and head-wind feeling at highway speeds.