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.

I had this same issue with the trans am a few months ago and i had a loose plug wire...

HELP!

 

Bad coil, cam sensor, crank sensor, or maybe injector?

 

New ngk tr5's gapped to .55 and i also checked for vac leaks. Its not a dead miss, I can pull the coil connections 1 at a time and none of the cyl's are missing more than others that i can tell.

 

Id wait for the tune,it will show up while on the dyno and the tuner should be able to pinpoint the issue easier.I think timing might just be a tad off from the 5.3 to 6.0. Only other thing I can think of check the plug wires.Alot of times they dont make the best contact on the plugs or the coil.I had alot of random misses using my old msd wires that could easily pull off and barely click on.

 

Well i got it fixed thank god, i put the coils off of the 5.3 on there. While i was installing the coils i noticed that the plug that go's into the coil harness was wet so i think they had some water in there before i pluged them in so i bet my coils are fine.

Anyway i just wanted to report back with the repair. I hate it when i find a thread with the same issues i have and no one ever comes back with a solution.

Thanks for all the help.

 

6.0 Gas engine This engine runs real rich and ruff. shows code 12. Installed new cap, rotor wires and plugs, Did not run any better after we installed the plugs cap and wires. It seems to run a little better after we installed a new map sensor but not by much. I do think the exhaust gaskets are leaking and they are getting replaced, could this be it or just part of it? Can anyone help me with a cure before i go throwing a bunch on money at it trying to cure the problem?
Hammer

 

Looks like you're already throwing a bunch of money at it

Post in the tech/ general forum. This thread covers a misfire on a 6.0 which does not have a cap/rotor to replace. Most likely a dying ign module, but do your research before buying anything else