Need some help with this. Just put another used ls1 motor (just bought long block out of 01 SS with 70k miles) in my 02 z28 6 speed. Stock motor other than shorty headers, Slp MAF, k&n air filter, and corsa catback exhaust ( also noticed the cats are hollow....on stock y-pipe )Last motor (72k miles) had piston in cylinder 7 coming apart. Have had trouble with these lean codes p0171 and p0174 and p0300 random misfire in last motor and now this one... SES light comes on for about a day then turns off for half a day randomly.. the car hesitates with a steady throttle acceleration.. acts like it wants to go fast, then slow like its being choked.. and heavily misfires at about half throttle or more.. not always but if engine has been idling for a few minutes or heat is high, it seems worse. Have had exhaust gaskets blowing out every time I change them ( the ones before cats on the headers on both sides of exhaust). Fuel filter changed like 15k miles ago. Also new plugs and wires.. Any input on this? Thank you a lot for reading this if anyone takes the time to...

Jeremy

 

Check the fuel pressure at the fuel rail.

 

Can you check the fuel pressure at idle and then while driving? Sounds like the engine (since both banks are affected, not just one cylinder) is going lean from lack of pressure. If it weren't for the fact that this is the second engine that has had this problem I'd say check for air leaks after the maf, but I'm hoping you'd have seen/fixed those on a swap.

Edit: Ninja'd!

 

Ok. Yes the intake is sealed well. No evident air leaks.. I tried cleaning MAF and also swapping to a stock one with no change. I'll go rent a gauge and check fuel pressure tomorrow if time permits and post my results. Do yall know what the pressure is supposed to be @ idle and WOT?

Jeremy

 

The fuel pressure specification may vary somewhat by year/model, but for my 2005 LS6 the specification is 55-62 psi with the ignition ON, but engine OFF. The service manual diagnostic procedure does not include a pressure check with the engine running. It does call for checking fuel trims with GM TECHII scan tool under various operating conditions.

 

Ok thanks a lot.. Wasn't able to check fuel pressure today.. Hopefully tomorrow since it's my day off. PS: I do have a scanner capable of monitoring fuel trims. I don't really know much about it though :/

Jeremy

 

Bumpppppppp.. I apologize for taking so long to post after I fixed the problem. But it was the SLP MASS AIR FLOW SENSOR! (MAF). IT WAS CAUSING THE LEAN CODES. I swapped it with a stock ls1 MAF and wala! No more codes. Been clear of the SES light for over a month now. I hope this helps someone in the future with this problem! # Thanks for the help guys.

- Jeremy