I'm trying to diagnose a problem w/ a 5.3 truck engine that is in in a Jeep wrangler. It is running a flashed F-body PCM running the 5.3 program.

When you rev it to about 2k + it revs somewhat smooth but you can hear a change in tone every half a second

when you go to drive it, it bucks/surges and sometimes wants to die (mainly when you arn't on the gas and then give it gas)

I've check for vacuum leaks, I'm not perfect, but I'm sure I have cleared up any vacuum leaks. I checked the fuel pressure and it is getting over 50psi. I also switched out the throttle position sensor w/ one off another engine and it still does the problem. I also switched the MAF on it- still does the problem

what do you guys think I should do? could it maybe be one or two bad coils? anyone know how to checked the coils?

let me know anything you guys think I should try and I will, I need to get this thing fixed!

 

Scan and tun software? Could be a anything honestly...vacuum leak, fuel trims out of wack, air leak, spark tables out of wack, IFR out of wack, A LOT of possibilties...scan it and post it and your tune

 

I wish I had tuning software, the only scanner I have is OBD. Everything is normal with everything, except the oxygen sensors ST FTRM1 and 2 are jumping all over the place (going from -35% to +35%) I think the problem rests in the fact that it is a F-body PCM that the 5.3L program was put in. I think something got messed up with the tune

 

I was wondering if you found the issue. I am having a similar issue with a 5.3L I put in my 67 C10.

 

Do you have the temp sensor plugged in? If not, the motor thinks its still cold and its chocking itself.