ok first the short version.
car has a miss below 2000 rpms
once i hit 2000 she runs awesome
no SES light on.
if i sit at a stop light too long the SES light start flashing and motor trys to die. give it gas and it "fixes" it. light stops flashing and goes off, idles normally
any ideas?

the long version/ background
spun a bearing. replaced entire motor, heads, intake, forged internals, new block, everything. only thing i kept from teh old motor was the cam. everything else was upgraded.
car ran fine with break in tune. put final tune on.
ran great for about 3 weeks. then it started missing, VERY slight at first, hardly noticable. then got progressivly worse for 2 weeks. until finally i lost cylinder #1. plug was fouled. cleaned and replaced. ran great for a month.
then started this miss. it wont go away. same info as in the "short version" only below 2000. above 2000 at half throttle , WOT, whatever, it runs awesome. i checked the #1 plug again, it was allitle wet. cleaned and replaced. didnt fix. i swaped #1 & #3 injectors and replaced #1 & #3 coils. didnt fix. and its not fouling the plugs last time i checked.
its been about 2 years since this car has run right. im desperate now. does anyone have ANY ideas.
fuel? fire? a/f? tune?


:help: :sulk:

mods below
PERFORMANCE
LME Forged 347*Wiseco -2cc Forged Nitrous Pistons*Callies Forged Rods*MJ2 Cam(232/240 .607/.608 112)*Comp Cams Hardened Push Rods*Ported Oil Pump w/ High Pressure Spring*Isky Racing Valve Springs*Isky Racing Titanium Retainers*Stage 2 4.8L Heads*2.055/1.60 Ferrera Valves*Ported F.A.S.T. LSX 90mm Intake*F.A.S.T. 90mm Throttle Body*Custom Tuning by Mike *K&N FIPK*SLP 85mm MAF*SLP Long Tube Headers*SLP Off-Road Y-Pipe*Dynomax Bullet Muffler*Rear O2 Sims*NOS 5177 Nitrous Kit*CAGS Delete*Moser 12 Bolt Rear End*33 Spline Axles*Eaton Posi Unit*Richmond 4.10 Gears*Polyurethane Sway Bar Mounts* BMR Torque Arm*BMR DS Loop* Polyurethane Motor and Tranny Mounts*EGR Delete*Taylor 10.4 mm Plug Wires*A.I.R. Delete*RAM Powergrip HD Clutch*LS6 Master Cylinder*LS6 Slave Cylinder*Vented & Slotted Rotors*Hawk Brake Pads

APPEARANCE
Chrome 18” AR Rebel Wheels*SS Valve Stem Caps*Metallic Black Racing Stripes*Black Halo Headlights*Diamond Clear Corner Lenses*Stull Billet Grill*Carbon Fiber Altezza Taillights*Under Hood Mirrors*Billet Aluminum Clutch Reservoir Cover*Polished Radiator Support*Battery & Fuse Cover Mirrors*Painted Intake*Billet Aluminum Engine Caps*Painted Carbon Fiber Fuel Rail Covers*Chrome Bolts*Smoothed & Painted Interior Trim*Silver Face Blue Glow Gauges*Billet Aluminum Control Overlays*Billet Aluminum Gauge Bezel

STEREO
Panasonic CD Head Unit*Kenwood 3 Way Speakers*Pioneer 2 Way Speakers*ProBox*Two 12” Fosgate HE2 Subs*Jensen 500 Watt Amplifier*Custom Amp Rack






LME 347 Short Block
Fully Machined and Blueprinted
Wiseco -2cc Forged Nitrous Pistons
Callies Forged Comp Star Rods
GM Balanced Crankshaft
C&A Dura Moly Rings
Federal Mogal 152M Main Bearings
Clevite CB 663 H Rod Bearings
Dura Bond CH-10 Cam Bearings
ARP Main Studs
ARP Rod Bolts


Clearances
Piston To Bore: .0047”
Main Bearing: .0023”
Rod Bearing: .002”
Ring End Gap: .027”(Top) .019”(Second)
Rod Side: .022”
Deck Height: 9.225”
Quench: .039”

 

Valve springs....getting soft on you?
Check em out.

 

Really sounds like a leaky injector to me. It would flood at idle, but above 2000 when the fuel demand is higher it'll smooth out. I know you swapped 1 & 3 injectors. But have you pulled #3 plug to see if it's getting wet now? Good luck.

 

shouldnt be. there isky (cant remember the type)
and they only have about 4k on them. my last set had over 10k.
what makes you say valve springs?

 

this was suggested before, they said a stuck injector, the injectors are stock and pushing like 118% (i know i know but they werent broke so....)

yeah thats what was frustrating, after the swap. the #3 didnt get wet. and niether did #1, yet the miss was still there. but that was only after about a week of driving after the swap. havent checked them since. ill pull them tonight.
ive got a SLP 85mm maf ive heard of probs with them (tuning wise) any possiblilites there?

 

Ditch the 85mm maf... Go back to stock w/ screen... then tune...
JMO...

 

id rather not. im running a FAST 90/90 setup. and it ran great until the miss...

 

Dude - if you have all the mods listed and still running stock injectors, get new ones. You should be running something like 36lb injectors anyway, I'm sure others will correct me if I'm wrong.

Throw a new set of plug in there while you are at it. Stockers won't be that great with N20 anyway.

 

I had a similar problem a while back and it turned out to be hi resistance on some wires. Ohm your wires if you havn't, I'll bet at least number 1 is high.

 

yeah i know the old ones were still working fine so i didnt replace them (cheap ***) i think ive calculated for 42# the motor is getting a 250shot. thats what it was built for.
im running TR6s. there new as well. (well 4k now)

 

ive already replaced those too during the hunt for the miss. well i replaced #1 & #3 only.

 

Corey,
Have you put the thing on a tech 2 yet while its missing...Go through and kill each cylinder at a time and see which one is actually missing. If thats not it, im going with new injectors and a complete retune from stock..Something tells me after 2K that the lower values in the map and timing tables have been altered too much and the new person didnt catch it at first glance. Theres soo many possibilites and as someone pointed out earlier...its like throwing darts at a problem trying to diagnose something of this caliber over the net.

 

Check fuel pressure? Last fuel filter change? what code did ses light throw

 

you may not want to go back to the stocker(MAf) but run it for a while and see if it fixes your problem. Also some of the stupid fixes, the fuel filter, grounds, pinched or disconnected, vacum lines.

 

no i had the local shop put this thing back together after the fastech fiasco. and well havent exactly been happy. who has a this tech 2 magic machine? i also thought about a temp gun, may help me figure out which cylinder. my buddy has one and a live monitor scanner thing so i can watch the car and read the codes.
yeah his tuning skills i think are far from top notch. but on his behalf it was running good when it left. jsut doesnt last long.

 

Most High End LS1 shops will have the Tech 2....might want to visit Daniel at SQR for his thoughts. his good at diagnosing stuff and at least has the equipment to tune and diagnose with..lol Chances are good its mechanical issues with your car that is messing up the tune.

Do you still drive up on the weekends to visit. Give Daniel a shout and go see him with your car.