surging at idle

[rdanley]

needing some info on what causes the surging at idle. my 04.5 lly when at idle is suging it is not major but you can fell it and hear it. i just completed a 4k mile trip with my 16k trailer could have got bad fuel. or is it my edge juice, i did turn my juice back down to stock still got the same thing. i know i need to change the fuel filter i do have 13k on it. or is this a sign of injector failure. any help would be appreciated i dont want to go to dealer blind. thanks

[Kennedy]

Try the fuel filter first. 13k is pushing it in my opinion. Many have FELT changes in response after changing 6-8k fuel filters...

Typically, a cold surge or pulse is programming and a hot surge is the pump regulator, but if it is starving and foaming, the regulator cannot do it's job.

[rdanley]

THANKS KENNEDY i do usally change my filter at 10k like i said i just got back from a 4k trip and i was getting all sorts of different types of fuel being on the road. thanks

[rickdlance]

A plugged fuel filter on a LLY will set a code and put the truck in limp home mode. Also my LLY's get noticebly better MPG when the filter starts to plug up. I almost hate to change it. Have waited too long 2 times now. Would lead me to believe that reprograming the fuel curve would do wonders for fuel mileage. Is the problem at low rpm or at all rpm?

[rickdlance]

Sorry, just noticed the "at idle". Have you had it reflashed yet? Both my trucks had a low speed surge that the reflash cured.

[rdanley]

like you rick i have noticed better fuel mileage, i went to my dealer yesterday to get a fuel filter get this they till me the fuel filter are on back order from gm. anyway i could not find one at any of my local parts stores so i got online and ordered 3 from oil gaurd i hope they are good filters. i did have the reflash done about a month ago but the mech at dealer told me that gm is coming out with a new reflash for rough idle anyone know what the numbers are i thought i saw something about this here.

[OC_DMAX]

rdanley -

Oilguard just "re-sells" the Racor fuel filter (which is the same fuel filter the dealer sells). So you should be OK. As far a I know, there is only one manufacture of DMAX fuel filters (Racor). All others just re-sell (and sometimes relabel) their product.

[rdanley]

thanks oc i just find it funny that the dealer has something that is so simple on back order and i can go online and in just a minute find anything i need.

[OC_DMAX]

I agree!! The really sad part is the price mark-ups that the dealerships are getting on these parts. There is thread on in the Truck and Drivetrain portion of the forum where the cost of the NSBU switch for the Allison Transmission is discussed. One Chev Dealership wanted $250 for the part and someone else found the same part at an Allison Transmission Shop for $52. Everyone is talking about the price of fuel these days, but the local dealerships is where the price gouging is going on.

[ 11-06-2004, 06:00 AM: Message edited by: OC_DMAX ]

[Stephen1]

Get your software updated by a dealer. It happened on mine at idle. You could even see the tach move slightly.
The software update made it go away completely. My truck was built in February 2004.

Steve

[rdanley]

ya stephen i had the reflash done friday of last week it worked perfect. the claibrations i had done were:

engine operation p/n 1524557

engine p/n 1525549