The truck runs great when first starting up and driving, after 10 min a cylinder start to miss ...the same one ..I'm lost any ideas?

 

Injectors are always suspect on the 6.0.

 

Even if they are all new ?? Runs perfect after the engine has cooled back off ...but if I floor it ..it will haul ***

 

Which cylinder is missing/ which codes are showing?

Do you have a scanner to read live data?

 

I have a sct programmer , it's cylinder 4 ..every once in a blue moon 5.. they are 155cc injectors and a new ficm from kt performance here in central Florida. It will idle fine sometimes after sitting and idling awhile ..but as soon as there is a load on the engine when warm I get a miss on that or those cylinders, fuel pressure maybe?

 

Do you have ARP head studs? It isn't outside the realm of possibility that you have a bad injector, even if it is new. It probably wouldn't hurt to have a chem test done on your coolant to see if you have a bad head gasket, which may or may not be causing compression loss when under a load. My 6.0 ran fine until I towed and it started over heating with a bad head gasket. It never missed due to that. However, I did have to replace the injectors back in February. When they were failing it was intermittent where it would either run like a bat out of hell or it wouldn't.

My local shop did the chem test for free and it took about 5 minutes.

 

No studs ..just a programmer and injectors. Would a bad harness cause this ? Maybe after a lil heat on the harness it starts to fail. ..wot throttle runs and pulls great , but 1500 to 1800 bucks and jerks bad

 

Possibly or a FICM, but I see you have a new one. I'm just guessing though. Maybe move a the harness around at #4 and see if you can induce the issue under different conditions.

 

while rare on the 6.0, on my 6.4 I have a misfire when hot cuased by work rocker tips. My truck also runs fine at mid to high rpm's but in the lower power band the misfire is evident. I also get contribution balance errors.

 

You need an actual scanner, something like Auto Ingenuity or a Snap On Solus to buzz the injectors, but IDS or a clone would be better to also see an unbalanced contribution test to check the injectors. I would think there's a small outside chance it's the o-rings on that injector, either on the injector or the nipple cup, but that might would show up as an ICP/IPR% issue if it were bad enough to cause a misfire.

Short of trying to access the correct diagnostic tools, swapping the injector to another hole is a next step; that will let you re-ring it and check the wiring for it. The injector harness from the FICM to the injectors is important to check, a bent pin in one of the connectors or wire chaffing is common enough.

 

Before I tear it apart , would o rings cause this issue on the injectors?

 

Sorry just read the previous post