Engine/Transmission (1998.5 - 2002) thoughts on shuddering

[favord]

Any new thoughts on the dreaded shudder.



My rig will shudder slightly without a load in 5th gear when I really step on it and run up the boost quickly... the shudder seems to start when the boost hits 28#. With horse trailer in tow, I can feel the shudder bad when I increase the load (like up a hill, stiff headwind, passing vehicles) in both 4th and 5th gear. Again the shudder seems to come on when boost hits about 28#. I've tried "di-electricing" the connections without success. I've cleaned the IAT sensor a few times and have now relocated a brand new IAT to my BHAF without success. The shudder happens in warm and cold weather... not just winter as some have observed.



One observation... I blew an intercooler hose apart last spring while on vacation and it took the turbo out too. I had the turbo replaced with another stock HX35 but forgot to tell them to put my boost elbow in the new one so I traveled back home with stock elbow. My boost would only go up to maybe 26# but I had no shudder and the rig pulled great. Problem with this was it would spike the EGT pretty easy to 1200-1300 so I'd have to bac out of it. I replaced the boost elbow, get 34# of boost and a cool engine but it is back to shaking my teeth out under load/hi boost again... ????



I've read probably all the threads/ideas on the dreaded shudder and tried about all the fixes. Most commonly it seems to occur in rigs with a fueling/boost module (usually the EZ in most threads).



I'm not sure what my question is but... what the heck is this? This rig rips with tons of "get up and go" but that shudder is driving me crazy.



Doug Favor

Pocatello, Idaho

 

[Gary - K7GLD]

Dunno about the newer trucks - my '02 doesn't "shudder" - but my old '91 did when I first got it - especially at low speeds, like accellerating from a stoplite - drove a few others that did the same... Problem with those, was the center support on the 2-piece driveshaft allowed the shaft to flex under load - creating an out-of-balance condition that was very annoying - worn center support components will do the same thing. My problem with the old truck went away when I had a US Gear OD unit installed, which required conversion to a 1-piece driveshaft...



Food for thought?

 

[LSMITH]

I had a clutch do exactly what you describe way back when. It was the clutch slipping and catching.

 

[JTroiano]

My truck does the same thing. It is almost like it is cutting out for a split second. When I turn the power down it doesn't seem to do it. Usually only in fifth when really putting the pedal down. I wonder if it is the clutch slipping for a slit second? I couldn't feel it with the stock clutch because it slipped to bad.

Jon T

 

[favord]

When I first noticed this I did think drivetrain/clutch but I just don't think that's the source... seems like there would also be a problem just trying to get a heavy load rolling if it was the clutch. This typically occurs at 65-75mph on the interstate pulling a horsetrailer up a hill or something similar.



Also from reading all the threads describing this symptom the auto's don't seem immune from it. Still the clutch is something to consider - don't know if I want to put the bucks in replacing a clutch to figure it out though.

 

[JTBMC]

Mine also does this and its an Automatic, only pulling a hill with the horse trailer or the camper above 21#'s of boost and 70-75 MPH in or out of Overdrive, and it gets worst the higher the boost climbs.

I disconected the EZ from the Data link and it doesnt do it. Plug it back in and its back.

Brice with Edge Products told me it could be a malfunction in the boost fooler part of the EZ and had me send it in for a check up.

I've decided to go for an upgrade to the Edge Comp. I sure hope it gets here soon my truck aint no fun with out it.

TJ

 

[rubberneck]

not drivetrain

I wish it were drive line angles or whatnot, but thats all been gone over many times. Ive checked the angles, and my truck has done it since almost new. Not the clutch, as it seems to be worse at moderate throttle. No shudder at full throttle or very light throttle. Some trucks just have the shakes as i like to call it. Buddys wifes truck set up identical is smooth as glass. Mine is much worse as the ambient temps drop below about 55. Above 60 i rarely notice it. Last year when we were all scrambling for answers, marco (mad ecms) suggested it may be a timing mapping issue in the cummins programming. I tend to think he may be correct as most of the trucks seem to get worse when a timing box is added. The only thing i dont understand is why all trucks dont have it if it is a programming issue. Oh well guess some of us are just luckier than others Any way as stated before, my truck did it totally stock. Fully bombed it is much more noticeable. It is only under moderate throttle except when temps drop below 25 degrees, then it seems to do it almost all the time. It is the worst between 1700 and 2100 rpms. I have tried a VA, an EZ, a comp, and my current set up as well as different size injectors. Bottom line, it's in the truck not the add on's, they only seem to aggravate the situation. Ive had the truck reflashed to no avail. Next step i think may be to replace the ECM altogether. I have also wondered if it could be picking up some kind of interference throught the wiring harness kind of like some of the auto trucks get with the locking unlocking convertor issue. If the ECM doesn't work i may swap the harness. Dont know, as far as i know nobody really does. I haven't tried anything new lately because ive just gotten used to it. Doesnt seem to hurt anything, just annoying as all he11

 

[zstroken]

shudder

I notice mine in 5th and 6th gear. Shut the comp off and it goes away. I actually have it on 1x4 now and it isn't that bad. I have notice that when it is on 1x5 the shudder is there in 5th and 6th. Shut the comp off and turn it back on and it appears to go away for awhile. WHat kind of turn around on getting the comp serviced??

 

[PROSTAR190]

My truck did the same until the VP44 finally died at 156,000. New VP44 and no more shudder. My truck did this cold or warm.

 

[fj40charles]

Prostar,



How many miles with the shudder before the vp44 died? Mine will do the same when I nail the throttle on 3x3.



Thanks,

Charles

 

[PROSTAR190]

The best that I remember I put the PE on the truck between 60,000 to 80,000. That is when I noticed it . Towards the end of the VP44 I could notice the shudder without the PE on at all and sometimes the truck would act as if it were going to die and then run fine for days and start again. One day it did die wile going about 40 mph and I got it to restart and run rought for about 300yards and died for good.

 

[fj40charles]

Prostar,



Good to know. . just trying to figure out how much time I have before a new VP44 or P7100...



Thanks,

Charles

 

[favord]

Rubberneck - sounds like we're talking the same thing except my shudder seems most pronounced under heavy throttle (actually I can best correllate it to when boost is greater than 28#). I've thought about changing to the Comp for its adjustability and see if I can find a happy medium of shuddering I can live with but I'd really just like to figure out what the heck is really causing it.



I have worried the shudder is a sign of the vp44 on a slow death... . is the Blue Chip vp44 tester good for anything other than saying the pump is working OK "now"? Thought about ordering it to investigate the pump.



Should mention I've monitored my fuel pressures and they seem adequate. I'm not off the charts with HP (320 rwhp) but wonder if its a fuel delivery problem under heavy load... fuel pressure OK though... ?? Ray's banjos maybe?



Doug Favor

 

[favord]

Just remembered that on a long thread regarding the dreaded shudder someone actually replaced their vp44 and the shudder was still there. Soooooo, who's to know... . I'm still thinking it's some sort of timing issue from the fuel/boost module when the boost gets "up there".



I thought maybe moving my IAT to the BHAF would at least make the intake air temp constant and remove that from the "timing equation" so to speak but it hasn't seemed to help (truck seems to run really smoooooth though now except for the high load shudder)



Doug Favor

 

[rubberneck]

dfavor, yup, sounds like same issue. I dont think the blue chip tester will tell you much on this. we have used the tester to verify nuked injection pumps that had the dreaded seized rotor. Im not sure if you could really use it for much else. Any way, last year there was at least 2 different guys that had their vp44 replaced due to the shudder. If i remember correctly, one said it helped the other said it didn't. I just kind of figure at this point, there is no point in sweating it if it dies, it dies. But the darn thing runs great besides. Oh yeah, i have also monitored my fuel pressure and all was good, i could not correlate the shudder to the fuel pressures. Temperature seems to be the only thing that i can pin down as a contributing factor.

 

[Summit]

your bummin

dfavor1, i live just up the road from you and i havent found a cure yet, 2 years and 75,000+mi. i can say that it's gotten worse over time, MUCH worse i've spent BOOKOO time&money trying to figure it out to no avail. i've been to two diesel techs that are very helpful but still no cure. my bucking gets so bad that usually in the mornings i can get my truck to die for 2-3sec. and run for 2-3sec. for miles if i keep it bucking. (how pathetic!!) . towing a load from I. F. to Poky is so bad that i have to alter my speed 65-80 so i can run it to the floor for a while then coast for a while otherwise you honestly can NOT stand to ride in this truck!!!



have changed; 4- inj. pumps, 3- lift pumps. 2-map sensor, 1-IAT, injectors atleast 10 times, turbo's,ECM's,injector tubes, totally removed fuel system-all hoses lines including fuel tank.



TRUCK DOES THIS WITH OR WITHOUT BOX!! BUT FAR WORSE WITH.



p. s. dfavor1 i'm going to P. M. you.

 

[Boost]

Last year on my 01 , when the temp dropped to below 50* I had the shudder. I replaced the following parts in this order and still had the shudder- lift pump, valve adjustment, IAT, APPS, coolant temp sensor, Map sensor, and VP44. Nothing helped until I removed either the dd2's or the EZ. Running either one by itself helped to make the shudder less noticable though it was still there. Running both together made it worse. Jump ahead one year and my 02 started shuddering when the temp dropped. Same exact shudder. I removed the 2's and run just my comp and it keeps the shuddering at a tolerable level. Maybe this winter someone will figure it out. But until then, debombing a little seems to help.





Rob

 

[favord]

Summit - sounds like you've worked it over pretty good looking for a culprit. Odd that with all the folks thinking about this we can't put a finger on it. Yes, you are close by and we might have to go for a ride and make sure we are having the same thing.



Just saw another recent post since this one describing an engine stumble that I think is the same thing.



It's gotta be something fixable doesn't it... ???

 

[CRegal]

I just noticed the same shudder a few weeks back. But after getting the thing good & hot no shudder. This is the 1st time I ran the truck with the dd3's in cold climate, last year on the comp settings 5/5 it ran fine no shudder. Mine isnt 2 noticeable yet, just a tiny lil bit that I would only notice due to be the one who always drives the truck. I really hope it doesnt turn into sumthing alot worse.

 

[favord]

Went for a trip with horse trailer in tow this weekend and here's what I've noticed:



As soon as I hit 26# boost the shudder starts and the tach very slightly starts to wiggle around, more like vibrate. If I "feather" the throttle to hold the boost between 26-30# the bucking really gets going and the tach wiggle gets slightly more pronounced (stays within a 100rpm range). If I back out slightly to hold it at about 25# it runs real smooth. If I peg the throttle as soon as the bucking starts and jump up to 30+ boost it runs pretty smooth too. I literally had it to where I could very slowly roll up the throttle watching the boost gauge and say its gonna shudder... . "now" - as it hit 26#.



Soooo, what does this mean? Don't really know but I'm speculating in the 26-30# boost range the "system" is going through fuel/defuel/fuel/defuel cycles for some reason giving that shuddering sensation. I don't understand well enough the relationship between boost/timing/fueling/etc. and the sensors that transmit that data. I thought the boost module simply prevented defueling when boost got above 20#. Are fueling/timing adustments constantly being made over the engines entire boost range? Is the ECM the brains of the whole outfit that makes all these adjustments? If not, which module is?



For now I think I'm gonna block off the orifice in my boost elbow... seems to limit it to about 25#. It runs hotter but I can still get down the road much faster than I really should be driving with horses in tow!



Thanks for any thoughts or info. on this... I really do think it has something to do with boost/timing/fueling relationship.



Doug Favor