i've been datalogging today and last night and i'm getting knock retard at low rpm low throttle and slight load like small inclines and such. WHY? full throttle no retard. and one more ?? i just installed new injectors when i'm tunning for the primary ve do i need to disconnect the maf or can it still be connected?

 

nobody knows or what???

 

What year is your truck? The early ones are known to have false knock.

And more importantly what are your mods?

 

alright its a 2004 4wd 4.8l. so far all i have is intake and exhaust basically. eletricfan descreened maf. here is the deal i have the following to be installed: t4/t04r turbo (65.5 mm) dmax intercooler dmax turbo back 4" mandrel bent exhaust, ls1 heads with ls6 valve springs, arp head studs, and a few others i can't think of. well this was suppose to be installed a month ago. well long story short i it fell through but before it did i was prepping the truck for the mods buy installing injectors and what ever else i could just help things along. well it fell through but i still have the injectors installed and don't really want to pull them out if i don't have to. they are the 8.1 42# injectors. truck idles fine runs fine but the ltft when i log i keep getting like between 9 to 15 some stuff i just get like 4 or even 0 should just keep going up and up till they stay between +-4%. as far a knock retard goes do i bring those blocks down the amount of knock retard or 1-2* more or what.

 

I'm no expert on these things, but your 42# injectors may be causing the problems. Those are really big for a relatively stock 4.8L. Those are too big for my LQ9 6.0L. I assume your tuning yourself, as the info above seems really familiar when Nelson tuned my truck. See if you can't get a hold of Nelson on this one. Maybe he can tell you how you can program your pcm until you can get the rest of your parts together.

Jim

 

[QUOTE=4.8T]alright its a 2004 4wd 4.8l. so far all i have is intake and exhaust basically. eletricfan descreened maf. here is the deal i have the following to be installed: t4/t04r turbo (65.5 mm) dmax intercooler dmax turbo back 4" mandrel bent exhaust, ls1 heads with ls6 valve springs, arp head studs, and a few others i can't think of. well this was suppose to be installed a month ago. well long story short i it fell through but before it did i was prepping the truck for the mods buy installing injectors and what ever else i could just help things along. well it fell through but i still have the injectors installed and don't really want to pull them out if i don't have to. they are the 8.1 42# injectors. truck idles fine runs fine but the ltft when i log i keep getting like between 9 to 15 some stuff i just get like 4 or even 0 should just keep going up and up till they stay between +-4%. as far a knock retard goes do i bring those blocks down the amount of knock retard or 1-2* more or what.[/QUOTE

Do you have the 8.1 injectors out of a truck, if so they are more like 30lb's or are they the marine injectors?

 

here are my injectors
Part Number 17113739 (OE Part # 25176061) *** Direct fit for short G.M. LS1 SUV injectors ***
Static flow @ 37.95lb/hr @ 43.5PSI / 300KPa (4.31 g/s = 398cc/min)
Static flow @ 43.82lb/hr @ 58PSI / 400KPa (4.97 g/s = 460cc/min) *
Dynamic flow (2.0ms/10.0 ms(pulse width / rep rate)) 6.0 lb/hr @ 43.5PSI (0.748 g/s @ 300KPa)
Coil Resistance: High Impedance / High-Z (No ECM driver modifications required)
Ball/Seat Design with 3-Hole Diffuser Disc - Pencil stream
Click here for specs and dimensions (mini)
O-rings and Fuel Rail Locks Included
Silicon grease supplied to lubricate o-rings prior to installation.

could that be where i'm screwing up i tune for 42# injectors should i raise that up some??

 

Did you use the correct IFR for those injectors to start? If so, try adding a little fuel down there. If that doesnt clear it up, then try taking a little timing. If that doesnt help than you probably have false knock and should look for things banging around like exhaust etc.

 

yes i corrected the IFR. i pulled some timeing at the spot where i see nock but i have been hearing this funny noise at those rpm's i can't explain it real well it kinda like a rattle like something is loose but only at certain rpms. not realy an exhaust rattle sounds like more of a front of the eng rattle or vib. i pulled some timming last night and loged it on my way to work this morning i still got a little retard but not as much but i didn't seem to hear the rattle. it a bit cooler out today and its raining. any ideas?? has any one heard or maybe heard this type of rattle?? i've been wondering about it too. it seems like i only hear it at say from a stop when i'm taking of slowly or sometimes if i'm at a cruise no throttle then slowly accelerate.

 

I have the same thing from the way it sounds. I'll have to do more logs (I meant to do some today on my way to work), but I dont think it showed up as KR.