This is my first post. My truck is stock with the exception of a K&N air intake. I'm New to diesels so please be kind if this is a stupid question. I seem to get an intermittent rough idle. Not very rough, but enough to feel the truck shake slightly. It almost feels like the engine is missing once in a while. It seems to happen more often after comming to a stop in slow traffic. I also noticed that if I take my foot of the brake the truck seems to almost lurch forward unevenly. I hope these descriptions are adequate. There are no codes comming up. I've had the dealer check it out but they couldn't find anything wrong. I suggested to the dealer that perhaps it needs a software update, but was told that it already has the latest. Again this may be all normal but I wouldn't mind some reasurance, as this is my first diesel.

I've heard of people having problems with the filter oil off the K&N getting on the mass air flow censor. You might want to try cleaning it with carb cleaner and replacing the K&N with a regular paper filter, they work the best.

This is my first post as well. I have an 05 lly that is bone stock and seem to have that same problem. Its almost like a surging which u can feel as well as hear in the engine idle and seems to happen only when u are almost coming to a stop or just released your foot of the brake and haven't even touched the fuel pedal. I am not an expert by any means but I have a feeling it might be something other than the MAP sensor. By the way everyone here is great and thanks for all the great info :)

There is a dealer re-flash that will cure your problem. Just tell the dealer, that your truck is surging at stoplights.....they reflash the computer....Volia!

I have a similar problem 45k miles. I have airaid intake system, 4" exhaust turbo back, rims, and the edge. I just had 2 and 7 injector wiring harness replace by the dealer was fight.

I notice the rough idle when backing my boat up and hitting the brakes hard and quick.

I'm going to call the dealer about the re-flash. See if they will do it.

Dropping my truck off at the dealer tomorrow for the rough idle. I checked the balance rates and a couple were high. I told dealer about the rates and he says an update should fix it, hope he's right. I have 65K miles.

I have an 04 with a 6 speed, and am having the same problem, i think. The dealer just replaced the dual mass flywheel for the third time, which accented the rough idle by violently shaking the gear shift leaver. Otherwise, the dealers here say nothing appears to be wrong. My truck only idles rough when it is warm, like after a good run down the highway. Number 7 injector was replaced under warranty, but no difference. Good luck

My LLY idles rough too. I have tryied everything. Stock air cleaner, reflash, etc. No luck yet. Some of these LLY's have grimlens! Mine dosen't surge though, just vibrates @ idle.

I had what sounds like the same problem with my LLY. Had the reflash then they said it possibly was the tranny then one good mechanic said he had seen this before and he replaced the fuel pressure regulator. I believe it is electronically controled and this seemed to solve the problem.

Could also be bad fuel?? I have had the problem when I used to fill up at every Diesel station on the road. Now with the larger tank, I fill up at only one and the problam has gone away. The indicators were; rough idle and black smoke. Also could be leaking EGR valve, allowing to much burnt exhaust into the intake at idle.

I had what sounds like the same problem with my LLY. Had the reflash then they said it possibly was the tranny then one good mechanic said he had seen this before and he replaced the fuel pressure regulator. I believe it is electronically controled and this seemed to solve the problem.


BINGO! My bet is on the FPR also. I'm told most diesel trucks will surge a little when light brake pressure is applied due to the compression. Mine truck did it when new - I posted a question about it back then and was told it was "normal".

That said. My truck is getting worse though. I have developed a slight lope at idle (different than the "surge issue" as I had the reflash done for that quite a while ago).

Before reading this thread I posted these 2 threads in an attempt to diagnose my similar idle problem.

Thread #1 (http://dieselplace.com/forum/showthread.php?t=169140)

Thread #2 (http://dieselplace.com/forum/showthread.php?t=168336)

BINGO! My bet is on the FPR also. I'm told most diesel trucks will surge a little when light brake pressure is applied due to the compression. Mine truck did it when new - I posted a question about it back then and was told it was "normal".

That said. My truck is getting worse though. I have developed a slight lope at idle (different than the "surge issue" as I had the reflash done for that quite a while ago).

Before reading this thread I posted these 2 threads in an attempt to diagnose my similar idle problem.

Thread #1 (http://dieselplace.com/forum/showthread.php?t=169140)

Thread #2 (http://dieselplace.com/forum/showthread.php?t=168336)Its not a lobe or a surge. It's a rolling vibration. My engine never misses a lick, or changes pitch, and the rpm stays rock solid. I have seen trucks do the surge your talking about due to the regulator.

My fuel pressure regulator has been changed. Made no difference.

are you oiling the kn filter too much? that would be the only reason why you should have it go towards the mass airflow sensor. otherwise it is normal and just enjoy the duramax

Try as said above cleaning maf sesnor, and get a tech 2 or somone who ahs access to the like to check your balance rates on the injectors.

Its not a lobe or a surge. It's a rolling vibration. My engine never misses a lick, or changes pitch, and the rpm stays rock solid. I have seen trucks do the surge your talking about due to the regulator.

No offense, but we are not talking about your trucks symptoms here - trying to solve PPK's problem in his original post. Your problem may be different than his.

No offense, but we are not talking about your trucks symptoms here - trying to solve PPK's problem in his original post. Your problem may be different than his.Ooops:o:. I got this thread mixed up with another one. Sorry:) His does sound like the regulator. Im such an idiot!

Thanks for all your advice, and opinions. I'm going to have to have the regulator checked. That sounds like the most likely culprit. I'll keep you posted as to the results.