I have a 2002 GMC 2500 HD and what brought me to the forum in the first place was trying to research / self diagnose my idle surge. Having searched around and read, it seems that I have whats been called "lopey Idle". I - and sorry to rehash here but I want to be clear - when I come to a stop and sit in gear(drive), my idle will start to fluctuate (surge) and if I let off the brake just slightly the truck will kind of buck - which is fun when I'm trying to hook up the trailer.


Anyway finally a question - This condition always goes away when my engine temp passes 180ish - not much ish - just as good as I can tell with the dash temp gauge. If it is the pressure regulator why is it temperature dependent?? Other then this it runs smooooth no smoke no other symptoms

Sounds like a fuel pressure regulator.

Yes, from how it acts and from what I have read it seemed it had to be the regulator or pump. The part I don't understand is why everything is ok after my temp get past half way. I would think it would do it other time also. Maybe the temp of the fuel or other sensors effects it.....still trying to figure it out http://www.dieselplace.com/forum/smileys/smiley24.gif. thanks.....Bill

Mine did that. Socaldieseltech repaired mine and haven't had it since.

Several others on here have reported that symptom. Check with the dealer, a reflash of the computer may be needed.Edited by: marcdeluca

This has been refered to here often as "rough idle". My truck had the
smae symptoms and all is well after all eight injectors were replaced. I
have since had the reflash just for the "peace of mind".

Well I can honestly say that I'm hoping the regulator and or reflash will fix this.......as I have no smoke, no diesel in oil, no coolant loss and runs fine when warmed up....I'm optimistic http://www.dieselplace.com/forum/smileys/smiley4.gif


ps ...if anyone can explain the temperature side of this I'd love to know. Someone else told me thay had the same same (fpr) but I forgot to ask the why why....thanks allEdited by: mightyvh

i have the same thing happening right now on my LLY, i took in for fuel
knock at about 1800 rpm and from a dead start rolling, but other than
that it was fine - they did a reflash to "fix that problem", and now
the dam thing is so loud before it warms up that its obnoxious, once it
gets to about 175 degrees, it goes away and runs perfectly fine, even
smoother than before, the dealer said it was a tradeoff and it was fine
but i dont buy that, it didnt do that before i brought it in but does
now so im a little heated but not sure what to do, it obviously had
something to do with the reflash, right ? and i know they have
another reflash for that problem as well, so i traded one for the other
- FRIGGEN GREAT ! any thoughts or ideas on this one ??

Mine goes under the knife (tech 2) tonight. I'll let you know how it turns out. Probably be a few days before I really know.....