BarnesCole

So i got the suburban over to a local tuner, and he started over from the stock tune. The truck idles and runs great under moderate to heavy throttle. I'm having a consistent/constant shudder(misfire) condition at light throttle when warm. Hesitation/stumble from dead stop and shuddering at cruising (50-60mph).

I looked over the new tune and it looks much more "similar" to the stock 6.0 tunes for an 09....so i feel better about that.

I've got an exhaust leak on the left side between the new header and y pipe (before cat). I'm gonna replace the ring type gasket and see if that fixes it.

The tuner mentioned that the cam wasnt quite phasing correctly, and said the phaser/actuator may have to be replaced. Being a new take out engine, i want to eliminate any other possible causes before replacing it.

I'm not getting any codes, but there are random misfires on all cylinders and an immature p0300 code. All the plugs and wires look good.

99 2500

Possibly an arcing pug wire?

BarnesCole

I thought plug wires at first too, but all cylinders were misfiring....and they were working fine before engine swap.

I've been in shop with it this afternoon...installed new exhaust gasket for driver side. Still have what seems to be an exhaust leak. It sounds like its coming from the driver side footwell when going down the road (reason i suspected flange gasket).

I did have an aha and a Holy S moment though. I grabbed the torque wrench to snug down the headers and all was good. I figured while i'm at it i'll double check the intake manifold bolts. They were barely hand tight. I torqued them down to 89 in lbs per Haynes manual. Went for a drive and most if not all of the hesitation and missing was gone.

I previously snugged them down by hand...guess i'm getting weak with age.

Gonna drive it a bit and hopefully make it back to dyno on Monday for final tuning.

BarnesCole

Still tinkering on the 6.0 to get it 100%. I've still got a stumble and random misfiring going on under low rpm high load. The timing jumps around a bit when this happens. The tuner that last worked on it thought it may be the cam phaser not working properly. I went back over everything to rule out anymore oversights like vacuum leaks, grounds, etc. It looks like i'll be pulling the cam and deleting the VVT afterall.

The engine runs great, has good compression, oil pressure...so i feel comfortable modifying it now. Even with the misfire i'm averaging about 16.5 mpg on highway.

New plans are custom grind compcam, new springs, pushrods, possibly lifters, VVT delete.

The spiral continues.

RWC

iTrader: (5)

Sounds like you've made a good choice with the 6.0L. If you have a tuning program like EFILive you are able to log the cam phaser position to confirm thats the problem before you take it out. If you can't, your tuner should be able too. Just log it at high MAP so its not affected by the part throttle extreme retard. I don't have a 09 6L tune file, but a 2010 6.2 doesn't advance until 4000 rpm except at PT. You might try putting the same values across each line in the cam phaser tables to make it easier to log. They're there for EGR type emission purposes. A good VVT cam that's setup right is becoming popular in the Camaro L99 6.2, some with over 500 RWHP with stock untouched heads & block thru a 6l80E.

BarnesCole

Thanks for the info RWC. I have HPTuners, is there any way to test the phaser with it? I havent seen anything that would allow me to directly command the phaser actuator.

BarnesCole

trying to upload .hpt file for current tune, but file over size limit...

RWC

iTrader: (5)

I don't know anything about HP Tuners, someone on here or on their website forum should know if it will log or make cam phaser changes. What does your tuner use to tune? Anyone you know with EFILive, they could log it for you?

BarnesCole

The tuner i'm using used my HPT since it was already licensed. I'm not sure if he has EFILive or not, i'll have to ask. He is the 2nd person to tune it, the first didnt work out so well (email tune).

I'm pretty old school i guess, the tuning(via computer) thing is totally new to me. But i'm learning. i'll search over at HPT and see what i can come up with.

RWC

iTrader: (5)

Looks like HP does support phaser tuning. I did some searching & found these;

VVT Tables

Variable Camshaft Question - VMAX

VVT tuning with compcams limiter - LS1TECH

Good reading for inquiring minds. I hope it helps you.

Ron