So I parked my truck overnight after having driven it about 60 miles round trip the day before. The round trip activity included blowing the tires off of it twice for the sake of realizing how good it's running since I finished cam, headers, intake, heads and PCM performance tune by Black Bear.

I had mis-wired the '06 - later efans blue and green wires in the PCM, corrected that did the PCM relearn procedure and truck started right up. Did the 60 mile round trip and reved the motor one last time before I shut the ignition off. This morning I go out and start it up and it's mis-firing bad in the header tubes like bullets ricocheting around in them. Motor starts right up, but sounds like crap.

Anybody have any ideas about what happened overnight? Haven't pulled the DTC's yet but I'm trying to get ahead of this one.

I feel like it's something simple....

V1

 

Your guess is as good as mine.

Could be simple, maybe a plug or a wire or who knows.

I'd figure out what cylinder(s) and go from there.

 

Any time you reset a PCM, It needs to relearn the fueling requirements upon start up.

If you start revving the motor and then shut it off it doesn't know any better.

Any time you reset the computer, whether clearing a code, pulling/ changing the battery, Etc. , You need to let it warm up on it's own under idle conditions from a cold start for 10 minutes.

That being said, make sure nothing is loose. If you can't pull the codes, pull the negative battery cable and let it sit for 10 minutes. Then reconnect, start it up, if sounds ok, let it learn on its own. If it's still misfiring after you start it, dig deeper. Either a lifter is collapsed, A plug is bad, or possible you damaged something.

I had this recently happen on a truck I working on and the lifter didn't pump back up. After checking everything mechanically, I figured it had to be a lifter. I poured some trans fluid in the oil and let it warm up. The lifter pumped back and it's fine now.

 

Brick,

Got ya. After fan wire correction at PCM and relearn procedure completed, I did start it cold, let it run and verified efan activation and noted temperatures when it kicked on. Also verified AC function and fan activation. Ran in the driveway for about 20 mins before the 60 mile round trip.

Lifters are new Brian Tooley. Plugs are NGK's for this 5.3 and wires are new Taylor 10.4's with Be Cool boot insulators. O2's are AC Delco. Coils are new AC Delphi round.

Like I said I haven't pulled DTC's yet but it's a definite random mis-fire. Motor is remarkably quiet since upgrades and runs like a beast. All great, no problems or mis-fires until it sat overnight and I started it this morning.

Weird...

 

Good deal.

Well, I hope its something simple.

 

God I love to report good news......

Traced noise / mis-fire to #6.. Pulled valve cover and immediately noticed exhaust rocker bolt visibly taller than the rest. No more than hand tight, enough that rocker was loose but not quite clacking.

Removed bolt inspected bolt and head threads, rocker, valve spring, retainer and valve tip for damage , cleaned and re-torqued bolt with a smidge of red Loctite. Called it good.

Removed cleaned, inspected and re-torqued balance of right bank rocker bolts as a precaution. All passed inspection and torqued to spec.

**LS1 Comp Cam rocker trunion upgrade and bolts.**
Don't know if this is a fluke or something that was missed during re-assy the first time. Bolt had no evidence of Loctite on it. Hmmm....

Field test

Wow! She's back.

Happy Happy....

 

Good Deal!!!