A strange thing begun to happen with my truck yesterday. When accelerating hard sometimes the truck will buck hard, like my foot had slipped off of the gas pedal or something then got back on it right away.


It would do it in any gear, and seemed to be less frequent if I would accelerate lightly, but it even did it a few times feathering the gas too.


Has anyone else had this happen? Any ideas what it might be?


No warning lights on the dash or anything. Does it with the Juice on level 0 or 5, makes no difference.


Cam

Was there related engine RPM change (a.k.a. clutch slippage) ?

No nothing like that, it even did it in 2nd gear once under fairly light acceleration.


It feels like it's running out of fuel or the ignition is cutting out. Very sudden and choppy.

Cam,


I have the Allison but my truck had similar symptoms after I got some bad fuel and it trashed my filter. New fuel and changing the filter fixed it for me. How old is your fuel filter?

Fuel filter is only about 5k miles old.. I did fill up at a place where I don't normally, but it is a fairly high volume place.


I'll try a new fuel filter and see what happens. That was my first suspicion as well, feels like it's not getting fuel or something.

mine will do that if i stay way too much power together.. also would do it running certain programs before fuel pump install.. check your fuel and your filter first... if running power box/programmer, remove and re-test.

It's probably the Hot-Sauce Flux Capacitor you have installed. http://www.dieselplace.com/forum/smileys/Cool.gif

My guess is his new secret dilithium-crystal engine enhancer conflicted with his roller muffler bearings which in turn caused his piston return springs to collapse. http://www.dieselplace.com/forum/smileys/Wink.gif


But thats only a guess. http://www.dieselplace.com/forum/smileys/Wacko.gif

Haved you scanned for codes yet ?? That's where I would start ...


Then dump the fuel filter ....


Any mods besides the current sig ??





Mac

I haven't scanned for codes, I don't have a programmer..


My mods (besides the ones in the sig) are the regular Juice/Attitude, AFE Stage 2 intake and straight piped exhaust.





I just installed a set of new Rancho 9000X's on the back on Friday, boy if I knew they were going to cause problems like this I would have bought bilsteins! Rancho is going to get a piece of my mind...http://www.dieselplace.com/forum/smileys/HiHi.gif

Then you obviously should have titled this thread, "RANCHO SHOCKS TOTAL PIECE OF CRAP!!!"


http://www.dieselplace.com/forum/smileys/HiHi.gif





I'd go with a fuel restriction, probably fuel filter.

AH HA!,http://www.dieselplace.com/forum/smileys/Geek.gif


You straight-piped it so you obviously blew the muffler bearings out.http://www.dieselplace.com/forum/smileys/Ermm.gif


Let me add my name to the "I think its the fuel filter" list.

I'll go with the fuel filter crowd myself.

Here's a not so good update.


The truck has sat all week, I haven't bought a new fuel filter for it yet, was going to do that tomorrow.


It seemed to be driving fine with the exception of the occasional bucking under heavy acceleration. Last time I drove it I kept my foot light and had no problems, no bucking.


I drove it tonight over to my buddy's place (5 minutes), let it idle in the driveway for a few minutes, when I got back in it the SES light was on. I drove it home right away and shut it off, then started it again to see if the SES light would come on again. It did. I shut it off and popped the hood, and I could hear a hissing noise coming from the fuel filter area, it was dark and I couldn't quite tell, sounded like maybe it was underneath it somewhere near the exhaust manifold.


(FWIW, the truck was running fine and the only indication of a problem was the SES light)


The hissing stopped before I could plug in my spot light. My buddy came over and I had him hold the light while I went to restart the truck. It now would only turn over for about 5 seconds then stop, no life, it wouldn't start. I tried a few more times and got the same results. I checked for any wet spots around the side of the engine bay where the hissing was coming from and everything looks clean/dry. I pumped the plunger on the fuel filter about a hundred times and tried to restart, still no luck. The truck has almost a full tank of fuel.


Any ideas what might have made the SES light come on?


I'm having it towed to the dealer in the morning. I wish I had a scan tool to see what code it threw.


BTW, first thing I did was unplug the Juice. It had no effect.

If it's sucking air it will stall and not start ....


I would have insured the water in fuel sensor and drain were tight ... Also filter itself and bleeder ...


I'll tell you for $350 bucks having the Predator in the backseat for these trouble shooting times is well worth the coin IMO...





Mac

It started fine this morning after sitting all night, and I drove it to the dealership. It bucked a few times on the way and my cruise control quit working for about 10 minutes.


They plugged in the tech 2 and I let them do their work, the mechanic working on it seemed to think it was the camshaft position sensor at fault here.


Mind you their diesel tech wasn't in today apparently so I don't know how much this guy knows about these trucks.


I got a 2500HD ext. cab long box 4x4 loaner so I'm not complaining http://www.dieselplace.com/forum/smileys/Cool.gif


They can keep it as long as they want while I put the miles on this thing instead.

does it have the edge attitude on it. if so mine did this also and then about a week later, the edge totaly died. when it is bucking keep on the accelerator and see what thr rpm's are mine would only go to 1500 - 1700. good luck probably the edge

I had that suspicion at first but after removing the Edge/Attitude the symptoms continued.

Camstyn


Mine was doing the same thing, but only with the Six Gun installed and pulling a load. It never cut out but I sure had the bucking. When it would start to buck, did you notice a puff of black smoke?

I wasn't watching for it when it was happening (too unpredictable, never knew when it was going to happen) but after it happened I glanced a few times and thought I may have seen a puff of black smoke. Might have been my imagination, but funny you ask.


What happened with yours?


It's still in the shop, I called about it yesterday and the guy at the service desk made some reference to the passlock ignition system, didn't make much sense to me but stuff like that gets lost in the translation between the mechanics and counter staff I imagine.


I'll hopefully find out today.


Cam

I just turned the SixGun to level 1 (stock) and it ran like normal. Banks has the SixGun now and are scratching their heads as to what the problem was. I don't have a clue as to what was going on, I've got 37K miles on the truck. The only reason I know there was black smoke is my wife was following me and got me to look. Let us know what the verdict is. I've got a thread going in the power/performance section now if you want to read about it go here http://dieselplace.com/forum/forum_posts.asp?TID=8823&PN=1Edited by: neverenuf

Could it be dry transmission splines?


They need to be greased periodically, or as the rear axil wraps under load, the yoke will not slide easily, as needed.

It's fixed now, just got it back this morning, they replaced the camshaft position sensor that seems to have done the trick.

Was that warrantee?

You bet, I kept my mouth shut about the power chip though.

Power chip? What power chip? How manu miles did you have on your truck?

I've got about 17k miles on it now. I've never heard of the cam position sensor being a problem with the duramax or of any failures besides mine, no idea what caused it..

Glad to see they were able to fix it.http://www.dieselplace.com/forum/smileys/Clap.gif


Cam position sensor related to the hissing sound coming from the fuel filter?

Yeah I don't know what that was about. I don't know if it was actually coming from the fuel filter, either, it was dark.. Just sounded like it was coming from that area.


I did prime the filter after hearing the hissing sound (pumped about 100 times) and the truck still wouldn't start so I don't think it was part of the equation.

Just as long as they fixed right the first time, really all that matters.

Hissing was probably the AC system...