Looking for some opinions on what this is.

When I am at a stop an slightly let me foot off the brake the truck pulses forward. I do not notice any change in RPM's or engine tone.

I am pretty sure it is not the rotors, because it does not do this while applying the brakes to stop, only after I have been sitting and let some pressure off the brake pedal to roll forward at idle speed.

Any help would be appreciated, let me know if I can tell you anything else to help diagnose this.

mine does the same thing. I think as long as it's not excessive it's somewhat normal. What causes it I am not sure of but my thoughts are that we may have a couple of cylinders not giving as much power as they should (maybe dirty injectors or something similar), maybe even close together in the firing order and so you feel it when your in this idle situation. I could be all wrong though. I do know I have been in other vehicles that do it also.

I had that same problem. My CP3 pump was defective. I went to All Season and had Tony put on an LBZ CP3 and will be going back to put on the fuel pressure sensor soon.

interesting, pulsing fuel pressure, that makes sense too. Maybe I need to check mine.

I would think you would hear the engine change tones or something. Was that not the case for you?

mine is like yours, there is no difference in idle rpm or tone- at least not noticable. It just sits and purrs like a kitten but I know what you are saying about the surge too. Let up off the pedal so the brakes are just holding and you feel the motor wanting to push forward in surges.

mine is like yours, there is no difference in idle rpm or tone- at least not noticable. It just sits and purrs like a kitten but I know what you are saying about the surge too. Let up off the pedal so the brakes are just holding and you feel the motor wanting to push forward in surges.

Yeah, exactly.

How long has yours been doing it?

Mine had no rpm change, but you could hear an engine tone change. As soon as the truck surged you could hear the tone change a bit.

mine has been doing it for a long time, year or better at least.

mines been doing it ever since i added a programmer and added power, when i take it off it goes away... i just always figured it was the tranny trying to move and without the extra pressure on the brake it was just sliping along.

I def have no change in engine tone at all. I have been paying really close attention to it, because I was worried it was something with the fuel system.

"Ace in the hole" - Has yours gotten any worse or just stayed about the same? Somehow I just started noticing it but it has not seemed to get any worse either.

mine has not gotten any worse, that's why I was not overly concerned. Like I said, it's been doing it for a least a year if not two and in every other aspect it runs fine.

ClassicChris- does it do it all the time or only occasionally?
You got me thinking I have not really noticed it lately. I just went to the post office and during that ride I was trying to get it to do it and really did not notice it at all.

ClassicChris- does it do it all the time or only occasionally?
You got me thinking I have not really noticed it lately. I just went to the post office and during that ride I was trying to get it to do it and really did not notice it at all.


I just drives me nuts not knowing what it is or what causes it.

I noticed it in my 04 from the day I drove it off the lot new. It only had 84 miles on it when I picked it up, so everything should have been in new condition. I attest it to the holding power of the transmission. If you ever look at a torque converter and how it works, the fluid passing through it is what makes everything work. Since the transmission does not go into neutral when the truck is stopped, it is possible that the torque converter is working just enough as fluid passes through it to transmit the power from the engine to the transmission and into the axle. By slightly pressing the breaks you are applying only enough pressure to hold the truck at a stop. Breaks work on friction and static friction does have a "break out" force. When the breaks release slightly, the engine rpm changes just enough to apply extra power steering pressure that adds additional breaking power through the hydro boost causing increased breaking pressure which stops the truck.

Push the break pedal down to the floor. If you have ever driven a truck or car with vacuum assisted breaks vs the hydro boost breaks you will know that it is much harder to push the break pedal to the floor on the vacuum breaks.

I eventually trained my brain to hold the break pedal down with a little more force to keep the truck from creeping up on the person in front of me.

Mine has done this since new. There is no change in motor noise, or speed. I always assumed it was in the torque converter.

I don't know if you guys are having the same thing happen though. It's not like the truck just wants to creep forward because of light brake pressure, it's more surges that you feel. You feel the truck surging, wanting to move a 1/2" and stop move a 1/2" and stop.... all while not changing the pressure on the brake pedal.

I don't know if you guys are having the same thing happen though. It's not like the truck just wants to creep forward because of light brake pressure, it's more surges that you feel. You feel the truck surging, wanting to move a 1/2" and stop move a 1/2" and stop.... all while not changing the pressure on the brake pedal.

Exactly, it is not just the "normal" creeping that all automatics do. I could imagine how it could be some variation or something from the torque converter. Like said earlier it is a pulse 1/2" stop 1/2" stop no engine tone change no brake pressure change. However if you are firmly on the brake pedal you cannot feel it at all, only when the brakes are softly applied.

I wonder if it is something in the transmission though. Thinking about it a more, I just changed the trans fluid a few months ago and I have not really noticed it since. I am not saying that cured it, it is just an observation.

I wonder if it is something in the transmission though. Thinking about it a more, I just changed the trans fluid a few months ago and I have not really noticed it since. I am not saying that cured it, it is just an observation.

I am thinking of doing that very same thing. What fluid did you put in yours?? Did you just drain the pan and refill w/ new spin on?

I drained and dropped the pan, wiped it clean and filled with fresh castrol brand fluid and new spin on. When I do it again though I am going to consider using the transynd fluid from allison, I hear it is great stuff but it's expensive too. If I remember it took almost 3 gal. the way I did it.

From what I understand, castrol makes/developed transynd for allison.

Mine actually revs up and down when sitting. If I was to lightly cover the brake it'd do the same thing but watching the tach tells me something else. It's done it for at least two years off and on. Not all the time, cold or hot out. Changed the trans filter at 25k, planning on changing fluid at 50k, I am still 10 away.

If you see or hear a RPM change then it is most likely your fuel pressure regulator....Heard many cases about this in the LLY as well as my truck....we have a tech 2 at work, I hooked it up and you could see the fuel rail pressure jumping all over the place at idle...

I did the plug remove and spin on filter change a couple of times. One time I did go through the trouble of pulling the lines and draining the trans cooler. Did make the switch to AmsOil synthetic trans flud for the allison. It seemed to help the shifts. It still creeps if you do not apply a hard break pedal. Mine will surge heavily if trying to do 5 or 10 mph through the parking lot when it is cold. But that is an entirely different issue.

I don't know if you guys are having the same thing happen though. It's not like the truck just wants to creep forward because of light brake pressure, it's more surges that you feel. You feel the truck surging, wanting to move a 1/2" and stop move a 1/2" and stop.... all while not changing the pressure on the brake pedal.

That's exactly what I have, but no change in tone or engine speed, which is why I think it is torque converter related. To me it feels like it couples and uncouples. Maybe some wierd fluid dynamics thing relating to low speed stator/turbine. I have no idea, but I always thought it was in the converter, and it has done it since new.

That's exactly what I have, but no change in tone or engine speed, which is why I think it is torque converter related. To me it feels like it couples and uncouples. Maybe some wierd fluid dynamics thing relating to low speed stator/turbine. I have no idea, but I always thought it was in the converter, and it has done it since new.

My original thought was something like what your are saying... just from the way it feels and I cannot notice any change from the engine.

I think I am going to try some fuel additive for safe measure and do a trans fluid change @ my next oil change. See what happens.

My truck has done it since I bought it with approx.28000 miles. (85000 now) No tone or noticeable rpm change; just a light surge at idle with light pressure on the brakes. I too would classify it as a surge, NOT a creep. It does it most of the time. Seems like the only time it doesn't do it is when I am trying to figure it out and have someone else riding with me to diagnose it. I'll be keeping an eye on this to see what you guys come up with.

my 04.5 in shop today for that problem.surging and at times idles rough.problem is showing on computer that it is getting alot of fuel feed to it and the computer is trying to adjust for it. they say its not the injectors. trying to get it to do while hooked to computer. found theres a problem but no fix yet.

Sounds to me like the typical lly regulator problem.As said before check with efi live or tech 2 and you will see your rail pressure jump around. The fix is upgrade to lbz regulator, but that is easier said than done as it is kind of a pain to get to.My 04.5 lly with 140000 has been doing it for a while. Some say a fuel system cleaner helps.

Sounds to me like the typical lly regulator problem.As said before check with efi live or tech 2 and you will see your rail pressure jump around. The fix is upgrade to lbz regulator, but that is easier said than done as it is kind of a pain to get to.My 04.5 lly with 140000 has been doing it for a while. Some say a fuel system cleaner helps.

I am starting to think you guys are dead on with the Fuel Pressure Reulator.

I was listening to the truck idle, when standing outside of it I can detect a very slight change in enigine tone, as someone else stated here earlier the tach tells a different story.

I think I am going to try some fuel additive for a "band-aid" and a new filter with my oil change this weekend. I will be sure to post the results......would be the greatest if a new filter and some additive fixed the problem :). But I think I will be doing some research on FPR replacement.

Anyone know of a how-to thread for this or have any tips for replacement/purchase of a FPR?

Is there any alterations to install the LBZ FPR, or is it a direct bolt-on replacement?

Ditto on what Chris said. I too have the surging problem, only does it occasionally but it's annoying. Does anyone know if this can be harmful to the injectors or other fuel system? I read on another forum that the FPR is a $375 part, around $800 for a replacement at the dealer. I just spent $750 on the EGR about a month ago on my out of warranty 04 with 53K miles. It's paid off, but with these "minor" maintenance costs, I might as well buy a new one with a PAYMENT!!

I had this problem before, too. Exactly how you said, when at a stop, it would pulse forward. I just took it to the dealer and the workorder said they put a new fpr and flashed it. it never came back since.

Ditto on what Chris said. I too have the surging problem, only does it occasionally but it's annoying. Does anyone know if this can be harmful to the injectors or other fuel system? I read on another forum that the FPR is a $375 part, around $800 for a replacement at the dealer. I just spent $750 on the EGR about a month ago on my out of warranty 04 with 53K miles. It's paid off, but with these "minor" maintenance costs, I might as well buy a new one with a PAYMENT!!


I was wondering this as well.... does it damage anything else??
Especially concerned about the injectors not getting enough fuel/lube.

Ditto on what Chris said. I too have the surging problem, only does it occasionally but it's annoying. Does anyone know if this can be harmful to the injectors or other fuel system? I read on another forum that the FPR is a $375 part, around $800 for a replacement at the dealer. I just spent $750 on the EGR about a month ago on my out of warranty 04 with 53K miles. It's paid off, but with these "minor" maintenance costs, I might as well buy a new one with a PAYMENT!!


Any Ideas if this damages the injectors or CP3??

Mines been doing this since I bought it but I thought it was normal, mine also seems to get a surge while coming to a stop sometimes (like someone blipped the throttle on me), also had it... not sure how to describe it, I started the truck, it idled for a couple min and when I shifted it into drive (at still nomal idle) it was like it was running 1500-2k rpm and the TC locked all at the same time (glad I wasnt parked to someones nose). It seems to run and shift fine for the most part, I've been checking it for codes regularly with the stealth 2 but never have had one. Does this indicate anything obvious or am I just not used to the dmax/alli? I assumed it was all normal due to the lack of codes.

Ditto on what Chris said. I too have the surging problem, only does it occasionally but it's annoying. Does anyone know if this can be harmful to the injectors or other fuel system? I read on another forum that the FPR is a $375 part, around $800 for a replacement at the dealer. I just spent $750 on the EGR about a month ago on my out of warranty 04 with 53K miles. It's paid off, but with these "minor" maintenance costs, I might as well buy a new one with a PAYMENT!!


Anyone know if this damages or can lead to injector damage??

The weird part is like today when I took the deezl out for a spin it didn't do it. Does anyone else have this happen intermittenly?

Good point, for all the posts on durability the amount of trucks that lost injector 7 you have to wonder if this has something to do with it.

Also, pump rub. I would think the worst thing for the tranny would be a pulsing of power against it.

I am an electrician, not a mechanic so I may be way off here.

The weird part is like today when I took the deezl out for a spin it didn't do it. Does anyone else have this happen intermittenly?

Good point, for all the posts on durability the amount of trucks that lost injector 7 you have to wonder if this has something to do with it.

Also, pump rub. I would think the worst thing for the tranny would be a pulsing of power against it.

I am an electrician, not a mechanic so I may be way off here.


nor am I haha but i'm thinking #7 failure is because of what the "ice pick" method is a fix for, probably due to lack of fuel lube as you said before. as for the fpr i think its just sending a surg of extra fuel not cutting it off completely? (again i don't know if thats a true statement) but if it is just dumping (or surging) extra fuel in then i don't think that could be too harmful unless you are running a higher tune.

Well, I sure hope it is not harmful, but it sure the hell is annoying. I was pulling my boat this weekend and it felt like I was running a full race cam in the damn thing. Jumping and lurching from idle. I guess I am going to have to bite the bullet (AGAIN) and take the damn thing to the dealer. This will make twice in 3 months OUT of warranty that this wonderful truck has cost me another payment. Hell, I would have thought that a 5 year old truck with 54K miles being paid off was a good thing, nope, it still requires a payment.....

Could be the FPR, the injector harness problem, and I know there was a reflash for the "parking lot surge" problem that was common on some of these trucks.

Well, I already had the injector harness replaced, FICM replaced, #2 & #7 injectors connections replaced all under warranty. A couple months ago it was the EGR valve OUT of warranty and now I guess the FPR OUT of warranty. Anybody want to start a pool to see exactly WHAT part will fail NEXT?

I just had my batteries tested, because it seemed like in the morning the truck was cranking slower.... sure enough I had 1 battery that was shot. Replaced the batteries....no more pulse!! Go figure. I have driven for 3 days 500+ miles and the pulse seems to be gone. (knock on wood). Now if I can just figure out what is causing the shutter/viberation (almost feels like out of balance tire) @ 45 mph is I will be all set.

I duuno but maybe you guys with this same problem should have a voltage test done on the batteries. I cannot believe that fixed the problem but it was gone insantly once the new batteries were put in.

I just had my batteries tested, because it seemed like in the morning the truck was cranking slower.... sure enough I had 1 battery that was shot. Replaced the batteries....no more pulse!! Go figure. I have driven for 3 days 500+ miles and the pulse seems to be gone. (knock on wood). Now if I can just figure out what is causing the shutter/viberation (almost feels like out of balance tire) @ 45 mph is I will be all set.

I duuno but maybe you guys with this same problem should have a voltage test done on the batteries. I cannot believe that fixed the problem but it was gone insantly once the new batteries were put in.


NEVERMIND........Its back, prob. shouldn't have said anything. So I guess I am going to need a FPR. Go figure.

However, I do think that using an additive seems to settle it down.

Anyone have the part number for the FPR??

Mine has been doing it on and off for about a year when I stand outside my truck I can hear the change in the motor as it surges very noticable with mine straight exhaust no cat no muffler 280,000 miles