garretthes

Engine is an LM7 transplant. We have had this problem since the swap and I really want to fix it. Engine runs OK until 4000 or so then it stumbles for just a second then runs on out to redline. It seems to take too long to shift as well so I find myself getting off the throttle. The computer was re-flashed by wait4meperformance.com. It had the same problem before when it was flashed by another guy. I'm sure the wiring is good to the MAF. We also tried another MAF. I'm also getting the following codes
PO171 and PO 174. I had a GM tech tell me the intake gasket was leaking when it was cold. Could this maybe be the reason for the lean codes?
I'm wondering if my fuel pump is putting out enough volume.

Old Geezer

iTrader: (3)

A fuel psi check when accelerating, and some datalogs will help find it...

garretthes

datalog? can i get those from my scan tool?

busta9876

iTrader: (3)

Was the PCM original with the engine. The LM7 used 3 different injectors from 1999,2000,2001. Probably not all of your problem, but could be some. Might check with who programmed your PCM, to check injector size. On the side of the injector is an 8 digit part#.

1999 and SOME 2000
part# 25317669. These will report 2.722 grams/sec or 21.6 lb/hr

MOST 2000
part# 25323974 or 25320288 - 3.125 grams/sec or 24.8 lb/hr

2001+
part# 25317628 - 3.180 grams/sec or 25.2 lb/hr

I know a pcm programmed for 01+ injectors on an engine with 99 injectors WILL run lean, long term fuel trims in the 12-18% range. I've seen this a lot programming pcm's where they were told they were buying a 01,02 engine (paying more) and got a 99. When I programmed PCM for a 99, it ran rough. I now check all injector sizes.

garretthes

The engine is 2004 with different CPU but it's the same type that came with it. I asked for a stock tune minus cats and security.

garretthes

Wondering if this problem is related to the inline fuel pump. Maybe it's not flowing enough causing the engine to starve.