2008 Suburban 6.0 Random Misfire

[bramage]

Frustration is starting to set in on this truck, ive searched a bit and have found nothing so here goes:

Bought the truck 6 months ago and on the 1200 mile drive home it gave me a flashing check engine light accompanied with Traction control light and an alternating message between Service Stabilitrak and Service Traction Control. Resulting code being P0300 (random misfire). It is now such that it misfires quite regularly if i demand fuel at low RPM. Above 4000 rpm it USUALLY doesnt give me any issue and pulls like a 6.0 should. I have swapped out the entire throttle body to net no change along with cleaning MAF. i have a pretty good OBD monitoring tool and it shows that the majority of the misfires are in a certain segment of the firing order but not necessarily specific cylinders. I havent ran that check recently so i forget (im pretty sure the bell peaked at 1+8). All connections into TPS seem sound and wires seem to be alright. Where do i look next? The weird part is really how well it runs over 4000

Truck has 202000 miles and no corrosion anywhere to speak of

[Formulabruce]

Could have intermittent bad coil pack, have seen this a few times. There is a way to test them, look on you tube I think A! auto has one

 

Stable track and traction control are Yukon, Suburban specific ( to best of my knowledge) and can be complicated.

[bramage]

bad coil pack would be specific cylinders failing would it not? also 2007+ HD trucks had traction/stability control (or at least Denalis did)

[Swimmer8366]

Check your fuel pressure check the intake gaskets. Swap coils around to see if it moves check injectors.

 

Sent from my Z981 using Tapatalk

[SILVER SLED]

Relearn or have the crankshaft position sensor relearned.

[Dixon700]

What gauge setups are guys using to check the fuel psi? There's a port on the fuel rail right? I've never paid much attention under the hood of this truck...

[davester]

On my '04, there's a port under a cap that unscrews on the right side fuel rail, the port itself looks like a bicycle tire valve, but when you push in the center, fuel squirts out...