Bucking/shudder part 2

[Walker]

[Since there's so many posts under both topics]:



I'm still a little confused as to the symptoms described by some as "hesitation, stumble, bucking, miss, and shudder. " One minute it sounds like everyone is describing it coming from the motor (fuel related), and the next from the drivetrain.



Here's my story: Last night I was hauling my 30' gooseneck with a load of cows 650 miles one way. Coming east through New Mexico on I-40 out of Abq. , I set the cruise on 75 and had no troubles keeping speed up some serious grades. PE Comp was set 1st on 1x1 (max temp 1150), then set it to 3x3 and it ran better and a little cooler.

Then later, I disengaged the cruise and that's when I notice the, what I call the "Bucking" symptom when accelerating up moderate grades. I was on setting 2x2 at the time, and the symptom definitely lessened when I turned off the Comp. But, I could also tell I was running with less power (fuel). When it started, I first slowly accelerated, then I let off the throttle slowly until the symptom went away. I didn't try accelerating "all the way through it" like some have described, so I don't know if that would have helped. But, I did apply a little and it only worsened.

The best way I can describe my feeling, is that it felt like I was rolling on "egg-shaped" wheels in the rear. I don't think it felt like a "hesitation, stumble or engine miss" like some have said. To me, it felt more like axel wrap like when in soft dirt or snow. Like the torque was twisting the spring packs and axle, causing the "buck" and then exaggerated when more throttle (fuel) was applied, but decreased as I let off.



The outside temp. was in the 30's for the whole entire trip. I've noticed some describe cold weather (not warm) as a condition to the problem.



This is the first time I've had this problem at all. My last heavy haul was in warmer weather, and I didn't have a problem. And I never have/had it without a load. Either my problem is just starting, or the cold weather/heavy load combo. is a possible cause/condition of the this problem (even though I didn't have a problem in the biggest hills of NM with the cruise set on 75).



I wonder if it may be gear related? Someone said no 4. 10 posters have replied to this problem. Also, what are the commonalities: manuals vs. autos, 3/4 vs. 1 tons, overload springs vs. not any, 4x4's vs. 4x2's, etc... So basically, I'm as confused and p'od as the rest of you about this problem. Hope it gets figured out soon.

 

[Summit]

or how about a "24valve hesitation/bucking/stumbling" forum? it sounds like there's almost enough of us to warrant one. my truck goes back again on wed. (bummer)

 

[rubberneck]

shudder

walker, i think the egg shaped wheel description is an accurate one. When i first encountered the "issue" at hand, it too felt like exagerated bucking from the trailer. this is not axle wrap, i wish it were that simple. i have traction bars (like the ones steve st L sells) and the issue is still there. I can do major burn outs with no wheel hop or axle wrap. I even put my truck on a dyno, and could duplicate the symptoms on the dyno. axle was not bouncing around, and neither was the engine for that matter. but i could feel it in the truck even on the dyno (twin roller style) Some have suggested bad motor mounts, or drive train twist. that is why i put it on the dyno to see if the engine was bouncing around, but nope, steady as a rock. there are in fact people with 4. 10 rear ends with the problems. I think less notice it because they are running higher rpm at same speed. in my case and several who have posted, the problem is in the mid rpm range, so maybe the 4. 10 guys are running a little higher rpm and dont notice it. I think this is a electronic issue with the pumps, either the solenoid is faulty, or the signal is being temporarily interupted to the solenoid, this may explain why the electronic boxes seem to exagerate the issue so much. dont really know, just thinking out loud at this point. there are several members going down the diagnostic path at this point. ( if i new for sure a new pump would fix this i'd pay for it out of pocket in a heart beat). maybe some of the members that get the vp44 replaced will post the results. hopefully it will give us some answers

 

[Ramafid]

What about engine timing? Most of the boxes increase the timing and could this be the problem? Are completely stock trucks that have no modifications having this problem. I've read that people that disconnect their boxes still have the problem but to a lessor degree. Once you add a box are you then "infected" for good? I never had a problem stock and it took about 6-7K miles after the box for the symptoms to appear. Hope this gets figured out soon.

 

[zman]

I experienced the exact same shudder that you guys are talking for the first time about 2 weeks ago when towing about 9k. Since it hasn't happened again, I didn't think anything about it until I saw this thread.



The truck sat outside the night before (usually parked in heated garage) and the morning temp was around 20*F. The shudder occurred around 1800-1900 RPM. Backing off the throttle made it go away, but more throttle made it worse (too chicken to accelerate through it).



At first, I thought it was the trailer bucking, but I could make it stop by decelerating slightly. My next thought was that it was axle wrap of some sort, since I could make it go away by decelerating and it got worse by accelerating.



After the transmission and engine warmed up, I didn't notice the shudder again on that trip. To this date, I haven't been able to figure out what caused it, but as stated above, it felt like riding on oval tires.



Steve

 

[JMarkos]

Just getting my e-mail notice. Has anyone tried changing their air sensor? was told today that could be a cause.







Also, is any of the other problem trucks from canada?

 

[Okie-Go]

I know the feeling

I started to post about this but found it here already. My 01 has done it a couple of times. I am at 2000 rpm(70) mph empty and it did it. It was like hitting the brake slightly with the fuel pedal still down, kind of a surging thing or a hard gust of headwind hitting the truck. I am on the small tank and that fuel has been in there for 3 months or longer. I will use it up and then refill with a good dose of cleaner. If that don't help a friend of mine said to unhook the ez and see if it does it again. It don't do it all the time just enough to kind of worry you. What does the air sensor thing sell for? I am NOT a mechanic and will be looking for answers here.

 

[Walker]

I'm leaving for my trip home tomorrow with trailer in tow (about 7k). It will be much warmer on the way home than on the way down. I'll post results about the haul home and the bucking issue this weekend.

 

[Mel Fuelling]

Has there been a serious evaluation of:

1) Adequate grounding of all elements of electronic fuel control?

2) How good are all connectors involved?

3) Are 1 and/or 2 being compromised at specific mechanical

frequencies or harmonics?

 

[Walker]

tow results

Coming home I tried all combos for causing the bucking shudder. I ran the Comp on 1x1, 2x2, 3x3 and off. I varied speeds on all types of grades and found the problem to definitely be in the 1800 rpm range while accelerating. It was also exaggerated by the Comp on higher levels.



Leaving, the outside temp. was 39, the high later was 63. As the temp got into the 50's, the problem all but disappeared with any combo of settings and speeds. It was still "slightly" noticeable, but nothing like at the colder temps. Even on the longest, steepest grades in the mountains of NM, with the temp in the 50's to upper 40's, the shudder was barely noticeable.



So, I'm guessing (don't really know a lot about this... ) but it would seem like the IAT sensor could be the cause. If the IAT senses engine temp. and it's drawing in colder outside air, or running at cooler temps. , doesn't it cut back on fueling? Then, with the demand for more fuel (and especially with the fueling box), the VP44 is not supplying enough fuel while accelerating.



What about guys running the winter fronts on the grille? Does that change internal engine temp? Do they notice the problem?



Like I said, I'm not IAT literate, so I'm just shootin' in the dark here, but just thought I'd post some results and ideas. We really need to get this one figured out.

 

[JMarkos]

I was thinking the same thing Walker, I had posted earlier in the fall that my head lights were flashing alot, I am convincted it is the grid heater. Coming home from snowmobileing last night we stopped for a burger, when we left it was dark and those things flashed for atleast 20 minutes, the engine temp guage was up to 190ish. If there is something that is telling the engine it is still cold then could it be affecting the fuel delivery? I know nothing technical about these sensers or what they do but this was my thoughts. What is the IAT(incoming air temp?)



Just so everyone knows the Edge boys are aware of the problem and are doing everything they can to try and help us, I talked to Taylor and Aaron last week, they are as confused as we are, but they are trying to help us out.

 

[tmacc]

I don't think it's the IAT sensor. I replaced mine back in the summer trying to get a little better milage. FWIW it didn't help. As I posted on another thread, I've had this problem since last Feb. The truck was bone stock at the time. I noticed it after I got the trans re-flash. (I don't think the re-flash had anything to do w/ it and it was probably there before I just didn't notice it. ) Took it back to the dealer and their solution was to re-flash the trans again. Typical results as you would imagine. Nada. It definately is temp. related. Because when temps went up in the spring, it seemed to go away. Now that it's cold it's back, only worse. The hesitation happens at 17-1800 rpm under light accelleration. Ever day, everytime. No codes set. Most noticable when towing.

 

[Ramafid]

I went on a day trip up to Buffalo NY ( had to see the snow) and it was bucking all day long. The rpm range was 1200-1800 just cruising along. When I accelerate I don't notice any problems, just under light throttle. This problem seems to be getting worse as time goes by. I had no problems just 6 mos ago. My grid heater cycles alot also. I stopped for fuel after running for 4 hours and when I started back up about 15 min later the grid heater was cycling. My engine was hot! I didn' think the grid heater was supposed to come on unless the temp was under 65 degrees, not 180! I also filled up with 45 cetane fuel and I think the bucking wasn't as bad as regular 40-42 cetane. I am also noticing more black smoke when I start the truck in cold and warm weather. I think I read a post a while back that when the injection pump is going bad it smokes more at startup? I hope this is not the case. Just more info for a puzzling problem.

 

[Big P]

I think we are starting to narrow down the symtoms as my truck reacts the same way, shudder under light to moderate throttle, between 1200-1900 rpm, 10-16lbs. of boost. As far as the heater grids go, I'm pretty sure they are supposed to turn off at 18mph regardless of the engine temp. I don't know about fuel pressure though, but I'll have a fuel pressure gauge in a couple of weeks. Man, it's getting to be alot of work finding and keeping up on all of the shudder related posts.

 

[tmacc]

MPagnucco reminded me of something I was thinking about today while the truck bucked for the upteenth time. Is anyone with a pusher pump having this problem? Ramifid, I know you have a single pusher pump, but is anyone w/ both pumps experiencing this?

 

[Walker]

tmacc,

I was thinking the same thing. If it's fuel starvation from the lift pump trying to draw fuel to far, instead of pulling it close to the tank (like the way it's supposed to be set up) or even pushing fuel, maybe that would affect the VP44 output under heavy load.



But, I still don't get the cold weather relationship, which I think (know) is definitely related, in my case anyway.



Let's hear from some "pusher pump" people.

 

[Ramafid]

I'm 100% positive that its not a fuel starvation problem because I have the lift pump back by the tank and fuel pressure at the injection pump never drops below 8-9 psi. Too bad we don't have the inline pump, I don't think we would be having these problems. Guess we'll just keep collecting info and hope for the best.