Running Lean!

Vehicle: 1998 Pontiac Firebird Trans Am Convertible LS1
Mods: SLP Lid, Cold Air Scoop, K&N Air Filter, LS6 Intake
Symptoms: Car is a little sluggish, big loss of power after 3000 rpms
Engine is throwing 4 codes: P0131, P0137, P0151, P0157
which I believe is saying all four oxygen sensors are reporting that it's running lean

I just got the fuel pump replaced about 3 weeks ago, because of the same problem. The symptoms seemed to have gone away for about a week. I then figured i would get the fuel filter replaced just to rule that out. Still running lean.

I decided to run a scan on my car to get a better insight in whats going on. Note, this was all done on a stockish tune, the only real change was transmission shift pressures and coolant fan temps. (I also tried the stock tune and still was running lean)

I haven't been able to check the fuel pressure, but if it was low, wouldn't the injector duty be high?

The first run has a few punches at WOT and the second run was idling in closed loop. These were both done using the default imperial config. When watching the closed loop scan, i noticed the STFT were constantly compensating for running lean. Can someone make sense of what is going on here? Maybe it's a bad sensor somewhere?

Thanks to all in advance

Those are low voltage codes, if you read the DTC it will tell you this.

Put a WB in it, check for leaks on the intake and exhaust, clean the MAF, and do not go WOT if you are lean. That will only make things worse.

That tune is not "stockish". That timing is WAY WAY too high. I suggest putting the stock tune in and doing some reading before you damage the motor.

FWIW, I seafoamed the car through the brake booster line the other day, and the next day it ran great and had all of its power back. The day after, it went back to having the same symptoms...

Ok, instead of starting a new thread, i'll revive this one. So since the first post, I have got the car looked at again and there were cracked fuel lines in the fuel tank. So that took my car from the 45 psi to 58psi once fixed. My fuel trims were maxed out at 25 before and now they are around 8.

So I was datalogging the car the other day, since it seems to intermittently have all of its torque. I noticed my O2s dropped to 0mv a few times throughout the run. Yes I notice there is some knock retard but I have fixed that. So my theory is that my O2 sensors are bad, causing it to dump fuel, and intermittently reading correctly.

Notice the big drop around frame 208 on one bank, frames 1255 and 1295 the o2 voltages actually drop to zero.

DFCO, normal when decelerating.

Russ Kemp

ah that explains it :banghead:

lol thanks