Check engine came on a few weeks ago and was flashing around 5100 to 5600 or so RPM's then last week it stayed on. My buddy hooked it up to the computer and was throwing a random misfire code. I cleared it out cause it was running fine. 3 nights ago it started flashing again and I was taken it easy and not turning it above 4 grand cause that's when it would come on this time. And its running real sluggish and pretty weak? Any ideas where to start? Its a CCSB 05 with a 5.3. CAi and custom tune. Thanks guys. Gonna be doing a 6.0 swap in a few months but still trying to get my heads and intake and everything I'm gonna do before I start. So I'd like to figure this out and have this 5.3 as a back. Thanks again guys

 

I'd check the plugs and the O2 sensors depending on how many miles are on it.

 

180,000

 

The o2 sensors were supposed to have been deleted in the tune but I'm not 100%sure. Getting weaker and weaker. Guess I'm gonna replaced the wires and plugs and see

 

If your O2S has been deleted as you say, that's probably why the engine is about dead.

Otherwise, replace the plugs and check Bank 1 and 2 Sensor 1's and consider replacing them.

 

the rear o2 sensors are the only ones that get deleted you still need to mantain your front o2's,
but i dont see how an out of wack a/f ration would create misfire, ide check for cracked, or wrongly gapped spark plugs. check all connections from the coil pack harness to spark plug wires as well

 

Check the cats too...

 

If it flashed its probably time to change spark plugs and wires. Have you ever changed them before?

 

Yes I have about a year ago. But before the tune. I'll get right on the plug and wire as soon I get off. Thanks guys. Just worrying me cause I have no passing power or anything and getting irritating