New LLY Calibration

[Jim Dandy]

...

NOTE: A new GMT800 LLY calibration will be available 9/4/2004 to correct the following 3 issues:
1) Rough idle, white / black smoke, and high balance rates
2) 1700

[Cliffee]

My dealer has told about this update also. Its supposed to be for my 03 which has the older motor. Are you sure its for LLY? I have slightly rough idle. They just replaced all 8 injectors. Definately, runs better but still a little rough idle at times. Seems worst when the temp goes above 100 here in AZ. I just hope this update doesn't screw anything else up. Other than a little rough idle truck is running great and I'm getting good milage!!!

[ 09-11-2004, 10:21 PM: Message edited by: Cliffee ]

[Jim Dandy]

The above was cut and pasted from a GM parts & service bulletin dealing with the injector order backlog for the LLY.

The injector order backlog for the LB7 was also addressed in the bulletin with no reference made to a new calibration.

PIP3129 (preliminary information) was issued 9-10-04. It states that the new calibration must be loaded on LLY trucks, then reevaluated, before injectors are replaced. Also, "Before any injector replacements a large fuel sample should be taken from the fuel filter and checked for contaminants or poor quality."

This PI is for LLY trucks only. I have both trucks and keep my eyes open for info pertaining to both.

[Cliffee]

Does your 02 have any rough idle issues?

[Jim Dandy]

No, its never been in the shop. Only 24k mi, however.

[FlyRod]

I have a 04 LLY with 4000 miles and have noticed the surging when driving slow through a parking lot. I wrote it off to a sensative fly-by-wire throttle position sensor. I also think my light throttle pinging is a bit exsesive even for a diesel. So far the engine idles smooth and there is no smoke. The only one that bothers me is the low throttle pinging. All other throttle ranges are quite (for a diesel). I find myself wondering if the pinging could be due to lean fuel mixture and be causing damage? If anybody takes a perfectly good LLY in for re-cal, let us know on how you come out. I am not brave enough to fix something I hope is not broke!

[More Power]

GM (and other high-pressure common rail diesel fuel injection users) inject a tiny amount of fuel before the main injection event in what is known as "pilot injection", to help quiet the diesel combustion rattle. If the LLY is producing more noise than it should during light-throttle use, it could be due to a more advanced injection timing or a change in the pilot injection.

Lean or rich doesn't necessarily apply to most diesel engines. Power is simply a function of the fuel rate. More fuel - more power (up to the engine's ability to burn that fuel), less fuel - less power.

MP

[mark45678]

I have a fuel rattle with my juice turned on ! it only happens around 160*~185*... I was hopeing gm would do something about this! The fuel rattle isnt as bad with juice off but its still there!