All right so I've got a 2001 trans am with a ls7. Car ran fine till the trans acted up so I pulled trans and dumb me left the plugs out and in Va that's not good.. So long story I had to pull heads, rods and pistons. Cam crank and timing chain stayed in motor... Every thing was torqued and lubed as required. So fast forward everything gets put back where it belongs and motor started right up.. So awesome put trans back in and that's where this story goes wrong... The car started but would backfire through exhaust for a min or so and clear up.. Then it would start up day one and run just fine. Then next day no good backfiring and glowing the headers ( dumping raw fuel in headers). Then start up just fine without changing a damm thing... So on so forth till one day it will start and run for 20-30 seconds then stops running and when it refires it will just back fire and glows headers.. I've cked all the small things grounds on the back of the head are good ( cleaned both head and terminals) , cked the plugs all was good, ck the tune. Even adjusted the lifter preload ( yes LS7 rocker arms are adjustable). Then I adjusted the tune put more gas in and took gas out, added timing (5deg) no changes and put it back to 8 deg. Nothings a miss and nothing has changed. Tune is a speed density so all but a couple of sensors are left. I have pin cked both the cam and crank sensor harness all was good. Put the PCM in another car and all was good. No water or fuel in oil. 60 psi fuel pressure. 40-60 psi for oil pressure. No odd or funny noises. Car doesn't run hot. Data logged and nothing in there( cam, crank, map iat, tps and injector duty cycle. I am at a loss of where to go next.... So any ideas out there...

 

Did you put a 24x reluctor on the crank or are you using a Lingenfelter converter box?

 

What ever is for a 01. Car has run and run well with all parts in motor.

 

Nice.

 

How long did you let the motor sit with the plugs out?

 

A year or so... Any ideas out ther as to the current problem?

 

Any ideas out there....

 

timing is off.

 

I've tried to change timing both ways up and down. What would cause the car to change it's trimming one day bad then the next good?

 

LS7 rocker arms are NOT adjustable. Your problem appears to be a burnt valve or carbon deposit build up.

 

They are adjustable and just had heads off car no deposits or bad valves.

 

Any ideas out there? Swapped PCM no change...

 

Check your fuel trims for ***** and gigs....