6.0 missing under load and at idle (SWAP)
 

I just swapped the 5.3 for this lq9 and motor sounds great no smoke, ticks but it has a slight miss at idle and it misses bad under a heavy load ( if you lug it when the converter is locked in 4th). I have installed new plugs and wires with no luck. Im not real sure where to go from here. I have no codes. The 5.3 ran perfect with no issues.



2002 lq9 120,000 miles



I am still on the 5.3 tune but correct me if im wrong but it should run fine with the same tune. I have read of quite a few people running the 5.3 tune with the 6.0. I will be taking the car this weekend to get the tune changed but i dont think it's going to fix my miss.



Only thing i can think of other than the tune is i have a weak coil. I used the coils off of the 6.0. My coils off of the 5.3 are at a friends house so im not able to swap them to see.

What do I do now???

I guess wait till you get your coils from your friends and go from there.