05 Lly Diesel - Hiccup / Pop Under Load

[Jettix2]

I've got an '05 LLY Duramax/ Alli with 98.5k on it. Normally spend most of my time on DieselPlace, but wondered if you guys could shed some light on this:

 

Truck has a Banks Intake, Exhaust, and Ottomind 6 programmer running on setting 4 (60hp tune) currently.

 

I just installed a new FPRV with an LBZ valve...this cured my P1093 code (would limp under load, going uphill). Also has a new fuel filter.

 

I've noticed now (truck is EMPTY) that as boost builds in 5th w/ OD heading up a hill, 55-60mph, as boost builds up to 12 or 13psi I'll occasionally get a HICCUP - HICCUP (pop-pop, the truck jerks a couple times) and then the truck will smooth out almost instantly. I can hear air/blow-off type noise from the engine when this happens.

 

No code stored, no SES light displayed.

 

It does NOT feel like a transmission issue..........feels like a split second loss of fuel pressure, or ingestion of air/dirt or something into the fuel rail.....

 

If the truck had a wastegate (the LLY does not), I would say it felt like a wastegate letting loose.....keep in mind that we're talking about 12 or 13 psi of boost here.........it'll hit 31psi on a good day and hold boost just fine.

 

I am running diesel w/ Diesel Kleen and I just put a qt of 2-cycle to smooth out a lumpy idle.

 

Could this be the FPR acting up? I was told it would cause a lumpy idle, but nothing else. Cracked fuel pickup in the tank? Bad injector?

 

There are three other guys with LLY's over on DP with the same problem, no answers.......some of them have the problem when towing, but all at same speed, same boost, same exact symptoms. I am assuming if I hook my 8500# TT up to the truck, I could get it to duplicate it easily, instead of the 1/50 times it does it right now.

 

Any thoughts?

 

Thanks! Ben

[gmtech4]

some additives are frowned on from GM so be carefull there and as for tuned up ,GM techs don't work on them to much ,road testing with a shop forman that has diesel experience is my thought to start ,they will want the tune turned off ,you may have warranty so be carefull there too

[Jettix2]

some additives are frowned on from GM so be carefull there and as for tuned up ,GM techs don't work on them to much ,road testing with a shop forman that has diesel experience is my thought to start ,they will want the tune turned off ,you may have warranty so be carefull there too

 

Ok, will do, thanks:)