LQ9 misfire.. No codes or CEL

[Chvy2NV]

What's up guys. I have a 07 NNBS with a Vortec MAX 6.0L and I seem to have a misfire at idle or reverse. Once the truck is going. It seems to be just fine. Ive had the truck 2-3 months now and Ive read endless threads and can't seem to pinpoint what could be causing this. I've had the truck plugged into a code scanner and have gotten 0 codes or CEL 's.
I called friend of mine which is a service manger at a local Chevy dealer and he says that it's completely normal. This is not what I wanted to hear... After trying to convince myself that this is "normal" for the past few weeks I took it to another friend of mine which has had his share of GM vehicles.
After sitting in the truck for 30 sec. He says to me. This **** is broken... There has to be a problem here. There's no way this drove off the lot like this. Which brings me to writing this.
What do you guys suggest I try next?

[GMCJOE]

Does it sound like it is misfiring? Or does it feel like it is by sitting in the cab? I thought mine was too, it felt like it had a ruff idle sitting still. I popped the hood and noticed my harmonic balancer wobbling a bit. Dealer also told me it was normal. You could clearly see the idler jumping around correcting it. Idiots!

[Chvy2NV]

I haven't really heard it. It's more of a feeling it thing. Truck just shakes kinda thing and the gauge fluctuates.

[GMCJOE]

Samething mine is doing. Start it up, pop the hood and look at the harmonic balancer. Probably has a slight wobble to it, and the tensioner pully will be jumping. My balancer was new on the motor when I bought the truck, been off 3 times since for warranty work. So, I got a defective one I need to replace. Update to let me know if you got the same issue. Mine is on a 5.3.

[buddy_1]

What is it idling at RPM wise? How many miles on it?

[Chvy2NV]

Truck has 100k. Idle is at 500 once it warms up. But initially it's pretty iratic. Which the more I read up on it the more others say it's completely normal. They say these motors make great power but the idle is crappy.

[buddy_1]

Couple of things to check. First, clean the throttle body real good. It should idle a little higher than that. If its really carboned up you will probably have to have the idle relearned afterwards or it'll idle too high. The other thing to check is the condition of the engine mounts. They are bad about collapsing and grounding out thus causing a rough idle that some think is a misfire.

[lowridergmc]

its normal.i remember seeing a a bulletin on it at one time.

[Special-Ed]

Motor mounts could cause this symptom as well.

[Chvy2NV]

Mounts are ok.

[bighaas79]

I was told in a GM class that it is a normal running condition because supposedly the factory programming actually has these motors running overly lean at idle to help to pass emmisions testing. Truth to that or not... not sure, but I know GM did alot of programming tricks with the 6.0's as far as torque management, and what not to make transmissions survive behind the amount of power these engines can put out. If they did infact program idle lean strategies for emissions it really wouldn't surprise me.

[Chvy2NV]

Would a tune fix this issue? Like a black bear tune?

[bighaas79]

A tune would probably help across the board so I don't see that it would hurt to try.