I've noticed on a few occasions that while at a stop and in gear that my idle rpm seems to surge -- tach moves just a touch -- and it happens 8~10 times before it smooths back out. Just yesterday it went through 2 cycles of surging. Sup wit dat?

I have seem this exactly. Take it out of gear and idle is rock solid. Put it in gear and it fluctuates just slightly, not enough to be a problem. I have not seen it cycle per se, but it does come and go. Right now it is gone. When it is happening, it will happen as long as I am stopped and in gear.

like at the drive thru, this seems to be where it happens to me or at least where i notice it.

The dmax has an issue with a slight idle surge. This can happen in gear or in park. The usual suspect is the valve that controls the fuel pressure in the common rail, it can flucuate at idle and cause slight different amounts of fuel to be injected causing a surge. I have lived with this for 90k miles to no major harm. Some additives seem to help reduce the frequency of surge but it's still there. Until something serious happens and it ends up in the shop I'm not going to worry about it.

I've lived with mine for 94k miles now and no problem. I should have mentioned it when I had the injectors replaced. Sometimes it does it and others not. I figure at 99k I may take it in to get the Fuel regulator replaced.

Is the fuel regulator covered by the 100,000 mile Duramax warranty?

Mine did this since new. No big deal.

It's probably the fuel regulator, but make sure the defroster is off before you commit yourself to the dealer. It cycles the A/C on and off as part of its demisting chores and will give a false impression of surging at idle.

TC

Mine will also do it at a stop if I don't have the brake firmly applied. The hydro boost pressure is pulsating. Later! Frank

I have noticed that mine does when the compressor cycles. That is if I have the A/C or the defroster it would give me a lopey idle--otherwise it was solid.

I looked at balance rates when this happened and my three injectors that are in the 4ish range will jump to the 5ish to almost 6ish while the idle ping pongs.

Now...with a lift pump...the idle will not ping pong but will be noticeably rougher and then clear up..balance go up and then back down by about the same amount as before the lift pump.

Is this normal..I did not think the compressor cycling would cause the idle to be unstable..much less affect the balance rates????

fuel pressure regulator...known issue

also an update for surgeing idle

like at the drive thru, this seems to be where it happens to me or at least where i notice it.
The earlier Quad tuners have been known to cause a surge, even at idle....if you have an early version maybe you should send it in to be updated, pretty sure it is free. I know the older tunes stacked better, but I hear the new tunes make more power, especially on the bottom end.

fuel pressure regulator...known issue

also an update for surgeing idle
does that mean it's going bad and should be replaced? Also, what's the "update for surgeing idle" about?

thanks!

bigd,

If your idle quality is good stock then I would rule out the FRPCV

The Quad 215 tuner you have can and will cause a cold lope idle........every truck that runs that particular v1.19 tune will have a problem with idle quality. I was told that after a while it would improve and was worse when cold.

If you need any more info. I would be glad to help.

PM me and I will set you straight.

T:cool: NY

Well I finally got mine in to my local dealer where I bought it and they did a quick fuel pressue test and saw the "fluxuation" and ordered a new "flux capacitor" AKA Fuel pressure regulator. Part will be in tomorrow, back on the road tomorrow night. Not bad, 1 day in and 1 day to fix. Service writer called and asked if I wanted them to put it back together so I could drive it home and bring it back tomorrow. I said "no you keep it and waive the $100 deductible" LOL Guess we will see if they do that or not ha ha ha

Nice to have the long warranty, but don't forget it's $100 deductible every incident after 36K. Way cheaper than paying the whole bill so I am not complaining.
I had forgotten about the tailgate cable recall so they will also do that while they have it. 45K on the truck and they said the injectors were fine. I told them that was due to the big yellow "Injector Cleaner" I have back there in the Left rear wheel well. Guy walked back, took a look and just smiled.

So far so good.....problem hopefully solved.

Made an appt. for mine this week as well. Wonder what the fuel pressure test costs if they DON'T find a fluxuation!

Well I finally got mine in to my local dealer where I bought it and they did a quick fuel pressue test and saw the "fluxuation" and ordered a new "flux capacitor" AKA Fuel pressure regulator. Part will be in tomorrow, back on the road tomorrow night. Not bad, 1 day in and 1 day to fix. Service writer called and asked if I wanted them to put it back together so I could drive it home and bring it back tomorrow. I said "no you keep it and waive the $100 deductible" LOL Guess we will see if they do that or not ha ha ha

Nice to have the long warranty, but don't forget it's $100 deductible every incident after 36K. Way cheaper than paying the whole bill so I am not complaining.
I had forgotten about the tailgate cable recall so they will also do that while they have it. 45K on the truck and they said the injectors were fine. I told them that was due to the big yellow "Injector Cleaner" I have back there in the Left rear wheel well. Guy walked back, took a look and just smiled.

So far so good.....problem hopefully solved.

Okay, I'll bite. What is the "big yellow Injector Cleaner"?:confused:

yea, had to think about that awhile, but I'm guessing it's a pre-OEM cat fuel filter (yellow?)

yea, had to think about that awhile, but I'm guessing it's a pre-OEM cat fuel filter (yellow?)
Thanks for the heads up.

From the polls and other information that I have found here, I do not believe that secondary filtration is the silver bullet to stopping injector failures. I guess that is why I did not automatically think "Cat Filter"...:rolleyes:

Thanks again.

Well, I'm getting pre-oem filtration asap after they un-jack-up my injectors. Figure what the H#LL, might as well. Ain't had it yet, run pretty clean fuel and this'll be the 2nd injector issue I have had. Can't hurt any.

Well, I'm getting pre-oem filtration asap after they un-jack-up my injectors. Figure what the H#LL, might as well. Ain't had it yet, run pretty clean fuel and this'll be the 2nd injector issue I have had. Can't hurt any.I understand and appreciate your decision:cool: . However, I have 45K miles on my 03 LB7 with no issues of any kind and no signs of injector problems:eek: . Not that a sample size of two (yours and mine) proves squat, but it does tend to agree with the trends of injector failure (or specifically the lack thereof)...

ON EDIT: I will be running dual filtration soon. As soon as I get my Black Stripe filters from Eric!:rolleyes:

):h

Got the truck back Tueday night, sure purrs like a big Kitty now. No more up and down revs, just steady idle. Used to watch the radio antenna wiggle around when the engine was surging, now the antenna stays still and smooth.

Yep the "Big Yellow Injector Cleaner" is the Nictane Cat Filter. Can't say it's the end all of injector problems, but if you run one and cut it open after 15K you will see a huge differance in what is no longer getting through to the OEM. If the OEM was only catching 60% and the CAT is getting 98%, then having the CAT in front of the OEM is a positive step. Cleaner fuel to the OEM means cleaner fuel to the injectors and that has to be a good thing. For the low cost of a pre-OEM it's cheap insurance. I have 1 more of the old OEM fuel filters then I will get a supply of the new 2005 OEM's for even cleaner fuel hopefully.

If I keep cleaning up the fuel I can buy #2 and burn #1 LOL ha ha ha

Everyone has to do what makes you happy. I believe the Pre-OEM Cat is beneficial and that's my opinion based on test done with the stock OEM which proved inadaquate in my opinion at the time. Now that opinion is enforced further by the new OEM that is suppose to address the poor filtering issues with the original OEM. Must have been a reason they redesigned that OEM filter. Soon we will get a chance to test the new filter and see what the changes in performance are.

Fuel On!

Got the truck back Tueday night, sure purrs like a big Kitty now. No more up and down revs, just steady idle. Used to watch the radio antenna wiggle around when the engine was surging, now the antenna stays still and smooth.

How often was your idle surging? I'm going in tonight and I'm wondering if it's worth mentioning yet.

thanks!
Don

My Idle Surge was once in a while maybe 2-3 minutes apart, then it just did it all the time. When I drove it in to the dealer I left it running so they could hear and see it. I had hoped they would find it annoying....closed in area where they do the writeups. They have 4 service writers there and each one said "yea I hear it" LOL I watched the tach, but it only flickered each surge. Some guys are reporting bigger surges (or was that urges) with 500+ rpm changes. Mine was not that bad yet.

If you have the surge and you are there at the dealer anyway. Let them fix it. Part is about $400+ and easy change if they have it in stock. Should be same day in and out if part is on hand. I just didn't want it to get worse and do something stupid like jump up the RPM all of a sudden and run into someone at a Red Light or dump a load of fuel in the crankcase or screwup an injector. Maybe all those things are not possible, but anyway, fixed now and she really purrs, almost like when I first got the truck.

When I dropped it off and the service writer came out to see what the problem was, I said "listen to it surging"! He said "yea I hear it, could be injectors we have problems with those", I said "I think it's the FPRCV" and he said "What"? I said "Fuel Pressure Regulator Control Valve"! (God, I love this site) He said "OK we will check it all out".

When he called me to say they had to order the part and did I need the truck back that night, I asked him "what was the problem", the guy said "It's what you said, that Fuel pressure thing". I laughed and told him to keep the truck and waive the $100 deductible. Well they didn't waive it, but they had a couple of recalls and took care of everything. One was the tailgate cables and the other I don't know what it was, but there were 48 (fasteners?) of them on the bill when I looked at it closely at home later that night. I'll have to ask them what it was when I go back with my wife's '02 buick for it's last check before warranty expires.

Good Luck with yours, I guess it's a common problem.

Got my truck back last week after a check for the idle surge. Dealer said that they hooked up a tech 2 and didn't find any problems. A few days later I changed my pre-oem fuel filter and you wouldn't believe the difference in performance! My occasional rough idle smoothed out and it runs like I put a chip on it. The ff only had 10k on it (I'll have to cut it open and check it out...

Well, I was researching to see what anyone had to say about the Quad as of late.....

Haven't heard anything good or bad so I'm looking here now.......BIGD....how's yours....anybody else having any issues or is there any current version readily available?......stacking?

Just trying to keep my options open.....:p:

Dipper, my surging idle was with no tunes in it

You know mine is still humming along and runs very nice. I did get a nice surprise from my dealer a week or so after they changed the Fuel Pressure Control Valve, someone called and said they were crediting my CC the $100 deductible! Not sure why, but I sure like it! Used that to buy some towing mirrors off an '05 to put on my '01.

Just shows clean living pays off.....:lol:

What about the versions....any new ones...advantages/disadvantages?

Thanks for the replies.