jonathan_ed3

iTrader: (4)

been battling these codes for a while. Car exhibits absolutely no drivability issues whatsoever. Just gets horrible MPG.

I smoked the intake system and found a nipple unplugged on the intake manifold. Plugged it, cleared the pcm.

Few weeks later the code comes back. Smoke it again, can't find anything. Smoke the exhaust, can't find anything except 1 tiny pinhole AFTER the driver o2 sensor. Cleared the codes.

Last week when I was tidying up my engine bay I noticed most of my exhaust manifold bolts were backed out. I figured this CERTAINLY had to be the issue. But remarkably when I smoked the exhaust previously it didn't leak here. Only thing I can think of is maybe it randomly only leaks when it's hot. IDK.

Anyway, tightened everything up. And cleared the codes.

1 code come back, and the other is continuously pending.

Now as I understand it, a vacuum leak should be identifiable looking at LTFT. If your LTFT drops as you raise RPM, that's a definite vacuum leak.

LTFT stays at 25% on both banks absolutely no matter what I do with throttle or RPM. I can't find anything with smoke machine. One time for a split second LTFT on one bank went to like 23%.

Codes always trigger at idle or right off idle.

Here's freeze frame data from the last code that triggered.

Looking for some input. This is seriously pissing me off. I want to get this sorted before I get tuned and continue to mod the car.

5.3, stock F body exhaust manifolds, LS1 intake, TSP stage 3 low lift truck cam, OEM LS3 injectors, LS3 MAF. Has a mail order "tune"/basemap from TSP.

scout2000

Hope there is something in here to assist, or at least food for thought.

I had those exact same 2 codes on my 2003 Gen-III 325 CID.

Mail order tune from lt1-swaps.com . Emissions and rear (but not front) oxygen sensors turned off.

I didn't have the fancy tool you had. I was using a low power bluetooth sending unit attached wirelessly to my Apple iPad.

My diag program stated verbatum "system too lean bank 1 & bank 2". Don't remember specifically which error code corresponded with which bank, but I had the same errors, P0171 & P0174.

Regardless, my issue turn out to be not one, but two bad oxygen sensors. I swapped out my oxygen sensors August 2016. The error code(s) have not returned. I've put 7000+ miles on then engine since that event, daily driver vehicle.

jimmyblue

iTrader: (11)

This could be false trimming from fouled O2 sensors,
one soot episode and you're done. But what is a "low
lift truck cam stage 3"? If that means high overlap,
maybe extra idle problems without the airflow benefit?

jonathan_ed3

iTrader: (4)

Replaced o2's this morning. Same issue. They flash from about 60mv to 800mv once warm (just like old ones). According to FSM o2's should flash between 200-800mv.

Fuel trim still pegged at 25% at idle. At cruise it's about 18%.

Regarding the low lift cam... idk what it means. That's exactly what TSP calls it.

https://www.texas-speed.com/p-5004-t...-camshaft.aspx

Absolutely no idle or WOT or partial throttle problems whatsoever. Just the constant codes and horrible MPG.

I want to get it dyno tuned/dialed in but I'm told I need to get the codes worked out first.

Any ideas guys?

G8One2

Do you have a PCV line in front of the MAF? How's you PCV system set up?

jonathan_ed3

iTrader: (4)

Brand new full LS6 pcv setup. New hose. New valve cover plug. New intake manifold gasket. Throttle body gasket.

G8One2

Im pretty sure that LTFT is a calculated percentage over time. STFT is looking good on your data logger, I would suspect it just needs tuned, especially if the fueling tables are not dialed in yet.